Image decoding method and device therefor

ABSTRACT

A method by which a decoding device decodes an image, according to the present document, comprises the steps of: acquiring a dependent quantization available flag about whether dependent quantization is available; acquiring a sign data hiding available flag about whether sign data hiding is available; and acquiring, on the basis of the dependent quantization available flag and the sign data hiding available flag, a transform skip residual coding (TSRC) available flag about whether TSRC is available.

BACKGROUND OF THE DISCLOSURE Field of the Disclosure

The present disclosure relates to an image coding technology, and moreparticularly, to an image decoding method and an apparatus thereof,which code flag information representing whether TSRC is enabled incoding residual data of a current block in an image coding system.

Related Art

Recently, demand for high-resolution, high-quality images, such as HighDefinition (HD) images and Ultra High Definition (UHD) images, has beenincreasing in various fields. As the image data has high resolution andhigh quality, the amount of information or bits to be transmittedincreases relative to the legacy image data. Therefore, when image datais transmitted using a medium such as a conventional wired/wirelessbroadband line or image data is stored using an existing storage medium,the transmission cost and the storage cost thereof are increased.

Accordingly, there is a need for a highly efficient image compressiontechnique for effectively transmitting, storing, and reproducinginformation of high-resolution and high-quality images.

SUMMARY

The present disclosure provides a method and apparatus for improvingimage coding efficiency.

The present disclosure also provides a method and apparatus forimproving residual coding efficiency.

According to an embodiment of the present disclosure, an image decodingmethod performed by a decoding apparatus is provided. The methodincludes: obtaining a dependent quantization enabled flag for whetherdependent quantization is enabled; obtaining a sign data hiding enabledflag for whether sign data hiding is enabled; obtaining a Transform SkipResidual Coding (TSRC) enabled flag for whether TSRC is enabled based onthe dependent quantization enabled flag and the sign data hiding enabledflag; obtaining residual information for a current block based on theTSRC enabled flag; deriving a residual sample of the current block basedon the residual information; and generating a reconstructed picturebased on the residual sample, wherein the TSRC enabled flag is obtainedbased on the dependent quantization enabled flag having a value of 0 andthe sign data hiding enabled flag having a value of 0.

According to another embodiment of the present disclosure, a decodingapparatus performing image decoding is provided. The decoding apparatusincludes: an entropy decoder configured to obtain a dependentquantization enabled flag for whether dependent quantization is enabled,to obtain a sign data hiding enabled flag for whether sign data hidingis enabled, to obtain a Transform Skip Residual Coding (TSRC) enabledflag for whether TSRC is enabled based on the dependent quantizationenabled flag and the sign data hiding enabled flag, to obtain residualinformation for a current block based on the TSRC enabled flag; aresidual processor configured to derive a residual sample of the currentblock based on the residual information; and an adder configured togenerate a reconstructed picture based on the residual sample, whereinthe TSRC enabled flag is obtained based on the dependent quantizationenabled flag having a value of 0 and the sign data hiding enabled flaghaving a value of 0.

According to still another embodiment of the present disclosure, a videoencoding method performed by an encoding apparatus is provided. Themethod includes: encoding a dependent quantization enabled flag forwhether dependent quantization is enabled; encoding a sign data hidingenabled flag for whether sign data hiding is enabled; encoding aTransform Skip Residual Coding (TSRC) enabled flag for whether TSRC isenabled based on the dependent quantization enabled flag and the signdata hiding enabled flag; encoding residual information for a currentblock based on the TSRC enabled flag; and generating a bitstreamincluding the dependent quantization enabled flag, the sign data hidingenabled flag, the TSRC enabled flag and the residual information,wherein the TSRC enabled flag is encoded based on the dependentquantization enabled flag having a value of 0 and the sign data hidingenabled flag having a value of 0.

According to still another embodiment of the present disclosure, a videoencoding apparatus is provided. The encoding apparatus includes anentropy encoder configured to encode a dependent quantization enabledflag for whether dependent quantization is enabled, to encode a signdata hiding enabled flag for whether sign data hiding is enabled, toencode a Transform Skip Residual Coding (TSRC) enabled flag for whetherTSRC is enabled based on the dependent quantization enabled flag and thesign data hiding enabled flag, to encode residual information for acurrent block based on the TSRC enabled flag, and to generate abitstream including the dependent quantization enabled flag, the signdata hiding enabled flag, the TSRC enabled flag and the residualinformation, wherein the TSRC enabled flag is encoded based on thedependent quantization enabled flag having a value of 0 and the signdata hiding enabled flag having a value of 0.

According to still another embodiment of the present disclosure, anon-transitory computer-readable storage medium storing a bitstreamincluding image information causing to perform an image decoding methodis provided. In the non-transitory computer-readable storage medium, theimage decoding method includes: obtaining a dependent quantizationenabled flag for whether dependent quantization is enabled; obtaining asign data hiding enabled flag for whether sign data hiding is enabled;obtaining a Transform Skip Residual Coding (TSRC) enabled flag forwhether TSRC is enabled based on the dependent quantization enabled flagand the sign data hiding enabled flag; obtaining residual informationfor a current block based on the TSRC enabled flag; deriving a residualsample of the current block based on the residual information; andgenerating a reconstructed picture based on the residual sample, whereinthe TSRC enabled flag is obtained based on the dependent quantizationenabled flag having a value of 0 and the sign data hiding enabled flaghaving a value of 0.

According to the present disclosure, the residual coding efficiency canbe enhanced.

According to the present disclosure, the TSRC enabled flag can besignaled when the sign data hiding is not enabled by setting thesignaling relationship between the sign data hiding enabled flag and theTSRC enabled flag, through this, when the RRC syntax is coded for thetransform skip block because the TSRC is not enabled, sign data hidingis not used to improve coding efficiency, and the overall residualcoding efficiency can be improved through reduction of the amount ofbits being coded.

According to the present disclosure, the signaling relationship betweena dependent quantization enabled flag and a TSRC enabled flag isestablished, and if the dependent quantization is not enabled, the TSRCenabled flag can be signaled, and through this, if the TSRC is notenabled and an RRC syntax is coded for a transform skip block, thedependent quantization is not to be used, so that the coding efficiencyis improved, and the overall residual coding efficiency can be improvedthrough reduction of the amount of bits being coded.

According to the present disclosure, the signaling relationship betweena transform skip enabled flag and the TSRC enabled flag is established,and if the transform skip is enabled, the TSRC enabled flag can besignaled, and through this, the overall residual coding efficiency canbe improved through reduction of the amount of bits being coded.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 briefly illustrates an example of a video/image coding device towhich embodiments of the present disclosure are applicable.

FIG. 2 is a schematic diagram illustrating a configuration of avideo/image encoding apparatus to which the embodiment(s) of the presentdisclosure may be applied.

FIG. 3 is a schematic diagram illustrating a configuration of avideo/image decoding apparatus to which the embodiment(s) of the presentdisclosure may be applied.

FIG. 4 illustrates an example of an intra prediction-based video/imageencoding method.

FIG. 5 illustrates an example of an intra prediction-based video/imageencoding method.

FIG. 6 schematically shows an intra prediction procedure.

FIG. 7 illustrates an example of an inter prediction-based video/imageencoding method.

FIG. 8 illustrates an example of an inter prediction-based video/imagedecoding method.

FIG. 9 schematically shows an inter prediction procedure.

FIG. 10 exemplarily shows context-adaptive binary arithmetic coding(CABAC) for encoding a syntax element.

FIG. 11 is a diagram showing exemplary transform coefficients within a4×4 block.

FIG. 12 exemplarily illustrates scalar quantizers being used independent quantization.

FIG. 13 exemplarily illustrates state transition and quantizer selectionfor dependent quantization.

FIG. 14 briefly illustrates an image encoding method performed by anencoding apparatus according to the present disclosure.

FIG. 15 briefly illustrates an encoding apparatus for performing animage encoding method according to the present disclosure.

FIG. 16 briefly illustrates an image decoding method performed by adecoding apparatus according to the present disclosure.

FIG. 17 briefly illustrates a decoding apparatus for performing an imagedecoding method according to the present disclosure.

FIG. 18 illustrates a structural diagram of a contents streaming systemto which the present disclosure is applied.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present disclosure may be modified in various forms, and specificembodiments thereof will be described and illustrated in the drawings.However, the embodiments are not intended for limiting the disclosure.The terms used in the following description are used to merely describespecific embodiments but are not intended to limit the disclosure. Anexpression of a singular number includes an expression of the pluralnumber, so long as it is clearly read differently. The terms such as“include” and “have” are intended to indicate that features, numbers,steps, operations, elements, components, or combinations thereof used inthe following description exist and it should be thus understood thatthe possibility of existence or addition of one or more differentfeatures, numbers, steps, operations, elements, components, orcombinations thereof is not excluded.

Meanwhile, elements in the drawings described in the disclosure areindependently drawn for the purpose of convenience for explanation ofdifferent specific functions, and do not mean that the elements areembodied by independent hardware or independent software. For example,two or more elements of the elements may be combined to form a singleelement, or one element may be partitioned into plural elements. Theembodiments in which the elements are combined and/or partitioned belongto the disclosure without departing from the concept of the disclosure.

Hereinafter, embodiments of the present disclosure will be described indetail with reference to the accompanying drawings. In addition, likereference numerals are used to indicate like elements throughout thedrawings, and the same descriptions on the like elements will beomitted.

FIG. 1 briefly illustrates an example of a video/image coding device towhich embodiments of the present disclosure are applicable.

Referring to FIG. 1 , a video/image coding system may include a firstdevice (source device) and a second device (receiving device). Thesource device may deliver encoded video/image information or data in theform of a file or streaming to the receiving device via a digitalstorage medium or network.

The source device may include a video source, an encoding apparatus, anda transmitter. The receiving device may include a receiver, a decodingapparatus, and a renderer. The encoding apparatus may be called avideo/image encoding apparatus, and the decoding apparatus may be calleda video/image decoding apparatus. The transmitter may be included in theencoding apparatus. The receiver may be included in the decodingapparatus. The renderer may include a display, and the display may beconfigured as a separate device or an external component.

The video source may acquire video/image through a process of capturing,synthesizing, or generating the video/image. The video source mayinclude a video/image capture device and/or a video/image generatingdevice. The video/image capture device may include, for example, one ormore cameras, video/image archives including previously capturedvideo/images, and the like. The video/image generating device mayinclude, for example, computers, tablets and smartphones, and may(electronically) generate video/images. For example, a virtualvideo/image may be generated through a computer or the like. In thiscase, the video/image capturing process may be replaced by a process ofgenerating related data.

The encoding apparatus may encode input image/image. The encodingapparatus may perform a series of procedures such as prediction,transform, and quantization for compression and coding efficiency. Theencoded data (encoded video/image information) may be output in the formof a bit stream.

The transmitter may transmit the encoded image/image information or dataoutput in the form of a bit stream to the receiver of the receivingdevice through a digital storage medium or a network in the form of afile or streaming. The digital storage medium may include variousstorage mediums such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, and thelike. The transmitter may include an element for generating a media filethrough a predetermined file format and may include an element fortransmission through a broadcast/communication network. The receiver mayreceive/extract the bit stream and transmit the received bit stream tothe decoding apparatus.

The decoding apparatus may decode the video/image by performing a seriesof procedures such as dequantization, inverse transform, and predictioncorresponding to the operation of the encoding apparatus.

The renderer may render the decoded video/image. The renderedvideo/image may be displayed through the display.

Present disclosure relates to video/image coding. For example, themethods/embodiments disclosed in the present disclosure may be appliedto a method disclosed in the versatile video coding (VVC), the EVC(essential video coding) standard, the AOMedia Video 1 (AV1) standard,the 2nd generation of audio video coding standard (AVS2), or the nextgeneration video/image coding standard (e.g., H.267 or H.268, etc.).

Present disclosure presents various embodiments of video/image coding,and the embodiments may be performed in combination with each otherunless otherwise mentioned.

In the present disclosure, video may refer to a series of images overtime. Picture generally refers to a unit representing one image in aspecific time zone, and a subpicture/slice/tile is a unit constitutingpart of a picture in coding. The subpicture/slice/tile may include oneor more coding tree units (CTUs). One picture may consist of one or moresubpictures/slices/tiles. One picture may consist of one or more tilegroups. One tile group may include one or more tiles. A brick mayrepresent a rectangular region of CTU rows within a tile in a picture. Atile may be partitioned into multiple bricks, each of which consistingof one or more CTU rows within the tile. A tile that is not partitionedinto multiple bricks may be also referred to as a brick. A brick scan isa specific sequential ordering of CTUs partitioning a picture in whichthe CTUs are ordered consecutively in CTU raster scan in a brick, brickswithin a tile are ordered consecutively in a raster scan of the bricksof the tile, and tiles in a picture are ordered consecutively in araster scan of the tiles of the picture. In addition, a subpicture mayrepresent a rectangular region of one or more slices within a picture.That is, a subpicture contains one or more slices that collectivelycover a rectangular region of a picture. A tile is a rectangular regionof CTUs within a particular tile column and a particular tile row in apicture. The tile column is a rectangular region of CTUs having a heightequal to the height of the picture and a width specified by syntaxelements in the picture parameter set. The tile row is a rectangularregion of CTUs having a height specified by syntax elements in thepicture parameter set and a width equal to the width of the picture. Atile scan is a specific sequential ordering of CTUs partitioning apicture in which the CTUs are ordered consecutively in CTU raster scanin a tile whereas tiles in a picture are ordered consecutively in araster scan of the tiles of the picture. A slice includes an integernumber of bricks of a picture that may be exclusively contained in asingle NAL unit. A slice may consist of either a number of completetiles or only a consecutive sequence of complete bricks of one tile.Tile groups and slices may be used interchangeably in the presentdisclosure. For example, in the present disclosure, a tile group/tilegroup header may be called a slice/slice header.

A pixel or a pel may mean a smallest unit constituting one picture (orimage). Also, ‘sample’ may be used as a term corresponding to a pixel. Asample may generally represent a pixel or a value of a pixel, and mayrepresent only a pixel/pixel value of a luma component or only apixel/pixel value of a chroma component.

A unit may represent a basic unit of image processing. The unit mayinclude at least one of a specific region of the picture and informationrelated to the region. One unit may include one luma block and twochroma (e.g., cb, cr) blocks. The unit may be used interchangeably withterms such as block or area in some cases. In a general case, an M×Nblock may include samples (or sample arrays) or a set (or array) oftransform coefficients of M columns and N rows.

In the present description, “A or B” may mean “only A”, “only B” or“both A and B”. In other words, in the present specification, “A or B”may be interpreted as “A and/or B”. For example, “A, B or C” hereinmeans “only A”, “only B”, “only C”, or “any and any combination of A, Band C”.

A slash (/) or a comma (comma) used in the present description may mean“and/or”. For example, “A/B” may mean “A and/or B”. Accordingly, “A/B”may mean “only A”, “only B”, or “both A and B”. For example, “A, B, C”may mean “A, B, or C”.

In the present description, “at least one of A and B” may mean “only A”,“only B”, or “both A and B”. In addition, in the present description,the expression “at least one of A or B” or “at least one of A and/or B”may be interpreted the same as “at least one of A and B”.

In addition, in the present description, “at least one of A, B and C”means “only A”, “only B”, “only C”, or “any combination of A, B and C”.Also, “at least one of A, B or C” or “at least one of A, B and/or C” maymean “at least one of A, B and C”.

In addition, parentheses used in the present description may mean “forexample”. Specifically, when “prediction (intra prediction)” isindicated, “intra prediction” may be proposed as an example of“prediction”. In other words, “prediction” in the present description isnot limited to “intra prediction”, and “intra prediction” may beproposed as an example of “prediction”. Also, even when “prediction(i.e., intra prediction)” is indicated, “intra prediction” may beproposed as an example of “prediction”.

In the present description, technical features that are individuallydescribed within one drawing may be implemented individually or may beimplemented at the same time.

The following drawings were created to explain a specific example of thepresent description. Since the names of specific devices described inthe drawings or the names of specific signals/messages/fields arepresented by way of example, the technical features of the presentdescription are not limited to the specific names used in the followingdrawings.

FIG. 2 is a schematic diagram illustrating a configuration of avideo/image encoding apparatus to which the embodiment(s) of the presentdisclosure may be applied. Hereinafter, the video encoding apparatus mayinclude an image encoding apparatus.

Referring to FIG. 2 , the encoding apparatus 200 includes an imagepartitioner 210, a predictor 220, a residual processor 230, and anentropy encoder 240, an adder 250, a filter 260, and a memory 270. Thepredictor 220 may include an inter predictor 221 and an intra predictor222. The residual processor 230 may include a transformer 232, aquantizer 233, a dequantizer 234, and an inverse transformer 235. Theresidual processor 230 may further include a subtractor 231. The adder250 may be called a reconstructor or a reconstructed block generator.The image partitioner 210, the predictor 220, the residual processor230, the entropy encoder 240, the adder 250, and the filter 260 may beconfigured by at least one hardware component (e.g., an encoder chipsetor processor) according to an embodiment. In addition, the memory 270may include a decoded picture buffer (DPB) or may be configured by adigital storage medium. The hardware component may further include thememory 270 as an internal/external component.

The image partitioner 210 may partition an input image (or a picture ora frame) input to the encoding apparatus 200 into one or moreprocessors. For example, the processor may be called a coding unit (CU).In this case, the coding unit may be recursively partitioned accordingto a quad-tree binary-tree ternary-tree (QTBTTT) structure from a codingtree unit (CTU) or a largest coding unit (LCU). For example, one codingunit may be partitioned into a plurality of coding units of a deeperdepth based on a quad tree structure, a binary tree structure, and/or aternary structure. In this case, for example, the quad tree structuremay be applied first and the binary tree structure and/or ternarystructure may be applied later. Alternatively, the binary tree structuremay be applied first. The coding procedure according to the presentdisclosure may be performed based on the final coding unit that is nolonger partitioned. In this case, the largest coding unit may be used asthe final coding unit based on coding efficiency according to imagecharacteristics, or if necessary, the coding unit may be recursivelypartitioned into coding units of deeper depth and a coding unit havingan optimal size may be used as the final coding unit. Here, the codingprocedure may include a procedure of prediction, transform, andreconstruction, which will be described later. As another example, theprocessor may further include a prediction unit (PU) or a transform unit(TU). In this case, the prediction unit and the transform unit may besplit or partitioned from the aforementioned final coding unit. Theprediction unit may be a unit of sample prediction, and the transformunit may be a unit for deriving a transform coefficient and/or a unitfor deriving a residual signal from the transform coefficient.

The unit may be used interchangeably with terms such as block or area insome cases. In a general case, an M×N block may represent a set ofsamples or transform coefficients composed of M columns and N rows. Asample may generally represent a pixel or a value of a pixel, mayrepresent only a pixel/pixel value of a luma component or represent onlya pixel/pixel value of a chroma component. A sample may be used as aterm corresponding to one picture (or image) for a pixel or a pel.

In the encoding apparatus 200, a prediction signal (predicted block,prediction sample array) output from the inter predictor 221 or theintra predictor 222 is subtracted from an input image signal (originalblock, original sample array) to generate a residual signal residualblock, residual sample array), and the generated residual signal istransmitted to the transformer 232. In this case, as shown, a unit forsubtracting a prediction signal (predicted block, prediction samplearray) from the input image signal (original block, original samplearray) in the encoder 200 may be called a subtractor 231. The predictormay perform prediction on a block to be processed (hereinafter, referredto as a current block) and generate a predicted block includingprediction samples for the current block. The predictor may determinewhether intra prediction or inter prediction is applied on a currentblock or CU basis. As described later in the description of eachprediction mode, the predictor may generate various information relatedto prediction, such as prediction mode information, and transmit thegenerated information to the entropy encoder 240. The information on theprediction may be encoded in the entropy encoder 240 and output in theform of a bit stream.

The intra predictor 222 may predict the current block by referring tothe samples in the current picture. The referred samples may be locatedin the neighborhood of the current block or may be located apartaccording to the prediction mode. In the intra prediction, predictionmodes may include a plurality of non-directional modes and a pluralityof directional modes. The non-directional mode may include, for example,a DC mode and a planar mode. The directional mode may include, forexample, 33 directional prediction modes or 65 directional predictionmodes according to the degree of detail of the prediction direction.However, this is merely an example, more or less directional predictionmodes may be used depending on a setting. The intra predictor 222 maydetermine the prediction mode applied to the current block by using aprediction mode applied to a neighboring block.

The inter predictor 221 may derive a predicted block for the currentblock based on a reference block (reference sample array) specified by amotion vector on a reference picture. Here, in order to reduce theamount of motion information transmitted in the inter prediction mode,the motion information may be predicted in units of blocks, sub-blocks,or samples based on correlation of motion information between theneighboring block and the current block. The motion information mayinclude a motion vector and a reference picture index. The motioninformation may further include inter prediction direction (L0prediction, L1 prediction, Bi prediction, etc.) information. In the caseof inter prediction, the neighboring block may include a spatialneighboring block present in the current picture and a temporalneighboring block present in the reference picture. The referencepicture including the reference block and the reference pictureincluding the temporal neighboring block may be the same or different.The temporal neighboring block may be called a collocated referenceblock, a co-located CU (colCU), and the like, and the reference pictureincluding the temporal neighboring block may be called a collocatedpicture (colPic). For example, the inter predictor 221 may configure amotion information candidate list based on neighboring blocks andgenerate information indicating which candidate is used to derive amotion vector and/or a reference picture index of the current block.Inter prediction may be performed based on various prediction modes. Forexample, in the case of a skip mode and a merge mode, the interpredictor 221 may use motion information of the neighboring block asmotion information of the current block. In the skip mode, unlike themerge mode, the residual signal may not be transmitted. In the case ofthe motion vector prediction (MVP) mode, the motion vector of theneighboring block may be used as a motion vector predictor and themotion vector of the current block may be indicated by signaling amotion vector difference.

The predictor 220 may generate a prediction signal based on variousprediction methods described below. For example, the predictor may notonly apply intra prediction or inter prediction to predict one block butalso simultaneously apply both intra prediction and inter prediction.This may be called combined inter and intra prediction (CIIP). Inaddition, the predictor may be based on an intra block copy (IBC)prediction mode or a palette mode for prediction of a block. The IBCprediction mode or palette mode may be used for content image/videocoding of a game or the like, for example, screen content coding (SCC).The IBC basically performs prediction in the current picture but may beperformed similarly to inter prediction in that a reference block isderived in the current picture. That is, the IBC may use at least one ofthe inter prediction techniques described in the present disclosure. Thepalette mode may be considered as an example of intra coding or intraprediction. When the palette mode is applied, a sample value within apicture may be signaled based on information on the palette table andthe palette index.

The prediction signal generated by the predictor (including the interpredictor 221 and/or the intra predictor 222) may be used to generate areconstructed signal or to generate a residual signal. The transformer232 may generate transform coefficients by applying a transformtechnique to the residual signal. For example, the transform techniquemay include at least one of a discrete cosine transform (DCT), adiscrete sine transform (DST), a Karhunen-loève transform (KLT), agraph-based transform (GBT), or a conditionally non-linear transform(CNT). Here, the GBT means transform obtained from a graph whenrelationship information between pixels is represented by the graph. TheCNT refers to transform generated based on a prediction signal generatedusing all previously reconstructed pixels. In addition, the transformprocess may be applied to square pixel blocks having the same size ormay be applied to blocks having a variable size rather than square.

The quantizer 233 may quantize the transform coefficients and transmitthem to the entropy encoder 240 and the entropy encoder 240 may encodethe quantized signal (information on the quantized transformcoefficients) and output a bit stream. The information on the quantizedtransform coefficients may be referred to as residual information. Thequantizer 233 may rearrange block type quantized transform coefficientsinto a one-dimensional vector form based on a coefficient scanning orderand generate information on the quantized transform coefficients basedon the quantized transform coefficients in the one-dimensional vectorform. Information on transform coefficients may be generated. Theentropy encoder 240 may perform various encoding methods such as, forexample, exponential Golomb, context-adaptive variable length coding(CAVLC), context-adaptive binary arithmetic coding (CABAC), and thelike. The entropy encoder 240 may encode information necessary forvideo/image reconstruction other than quantized transform coefficients(e.g., values of syntax elements, etc.) together or separately. Encodedinformation (e.g., encoded video/image information) may be transmittedor stored in units of NALs (network abstraction layer) in the form of abit stream. The video/image information may further include informationon various parameter sets such as an adaptation parameter set (APS), apicture parameter set (PPS), a sequence parameter set (SPS), or a videoparameter set (VPS). In addition, the video/image information mayfurther include general constraint information. In the presentdisclosure, information and/or syntax elements transmitted/signaled fromthe encoding apparatus to the decoding apparatus may be included invideo/picture information. The video/image information may be encodedthrough the above-described encoding procedure and included in the bitstream. The bit stream may be transmitted over a network or may bestored in a digital storage medium. The network may include abroadcasting network and/or a communication network, and the digitalstorage medium may include various storage media such as USB, SD, CD,DVD, Blu-ray, HDD, SSD, and the like. A transmitter (not shown)transmitting a signal output from the entropy encoder 240 and/or astorage unit (not shown) storing the signal may be included asinternal/external element of the encoding apparatus 200, andalternatively, the transmitter may be included in the entropy encoder240.

The quantized transform coefficients output from the quantizer 233 maybe used to generate a prediction signal. For example, the residualsignal (residual block or residual samples) may be reconstructed byapplying dequantization and inverse transform to the quantized transformcoefficients through the dequantizer 234 and the inverse transformer235. The adder 250 adds the reconstructed residual signal to theprediction signal output from the inter predictor 221 or the intrapredictor 222 to generate a reconstructed signal (reconstructed picture,reconstructed block, reconstructed sample array). If there is noresidual for the block to be processed, such as a case where the skipmode is applied, the predicted block may be used as the reconstructedblock. The adder 250 may be called a reconstructor or a reconstructedblock generator. The generated reconstructed signal may be used forintra prediction of a next block to be processed in the current pictureand may be used for inter prediction of a next picture through filteringas described below.

Meanwhile, luma mapping with chroma scaling (LMCS) may be applied duringpicture encoding and/or reconstruction.

The filter 260 may improve subjective/objective image quality byapplying filtering to the reconstructed signal. For example, the filter260 may generate a modified reconstructed picture by applying variousfiltering methods to the reconstructed picture and store the modifiedreconstructed picture in the memory 270, specifically, a DPB of thememory 270. The various filtering methods may include, for example,deblocking filtering, a sample adaptive offset, an adaptive loop filter,a bilateral filter, and the like. The filter 260 may generate variousinformation related to the filtering and transmit the generatedinformation to the entropy encoder 240 as described later in thedescription of each filtering method. The information related to thefiltering may be encoded by the entropy encoder 240 and output in theform of a bit stream.

The modified reconstructed picture transmitted to the memory 270 may beused as the reference picture in the inter predictor 221. When the interprediction is applied through the encoding apparatus, predictionmismatch between the encoding apparatus 200 and the decoding apparatus300 may be avoided and encoding efficiency may be improved.

The DPB of the memory 270 DPB may store the modified reconstructedpicture for use as a reference picture in the inter predictor 221. Thememory 270 may store the motion information of the block from which themotion information in the current picture is derived (or encoded) and/orthe motion information of the blocks in the picture that have alreadybeen reconstructed. The stored motion information may be transmitted tothe inter predictor 221 and used as the motion information of thespatial neighboring block or the motion information of the temporalneighboring block. The memory 270 may store reconstructed samples ofreconstructed blocks in the current picture and may transfer thereconstructed samples to the intra predictor 222.

FIG. 3 is a schematic diagram illustrating a configuration of avideo/image decoding apparatus to which the embodiment(s) of the presentdisclosure may be applied.

Referring to FIG. 3 , the decoding apparatus 300 may include an entropydecoder 310, a residual processor 320, a predictor 330, an adder 340, afilter 350, and a memory 360. The predictor 330 may include an interpredictor 331 and an intra predictor 332. The residual processor 320 mayinclude a dequantizer 321 and an inverse transformer 322. The entropydecoder 310, the residual processor 320, the predictor 330, the adder340, and the filter 350 may be configured by a hardware component (e.g.,a decoder chipset or a processor) according to an embodiment. Inaddition, the memory 360 may include a decoded picture buffer (DPB) ormay be configured by a digital storage medium. The hardware componentmay further include the memory 360 as an internal/external component.

When a bit stream including video/image information is input, thedecoding apparatus 300 may reconstruct an image corresponding to aprocess in which the video/image information is processed in theencoding apparatus of FIG. 2 . For example, the decoding apparatus 300may derive units/blocks based on block partition related informationobtained from the bit stream. The decoding apparatus 300 may performdecoding using a processor applied in the encoding apparatus. Thus, theprocessor of decoding may be a coding unit, for example, and the codingunit may be partitioned according to a quad tree structure, binary treestructure and/or ternary tree structure from the coding tree unit or thelargest coding unit. One or more transform units may be derived from thecoding unit. The reconstructed image signal decoded and output throughthe decoding apparatus 300 may be reproduced through a reproducingapparatus.

The decoding apparatus 300 may receive a signal output from the encodingapparatus of FIG. 2 in the form of a bit stream, and the received signalmay be decoded through the entropy decoder 310. For example, the entropydecoder 310 may parse the bit stream to derive information (e.g.,video/image information) necessary for image reconstruction (or picturereconstruction). The video/image information may further includeinformation on various parameter sets such as an adaptation parameterset (APS), a picture parameter set (PPS), a sequence parameter set(SPS), or a video parameter set (VPS). In addition, the video/imageinformation may further include general constraint information. Thedecoding apparatus may further decode picture based on the informationon the parameter set and/or the general constraint information.Signaled/received information and/or syntax elements described later inthe present disclosure may be decoded may decode the decoding procedureand obtained from the bit stream. For example, the entropy decoder 310decodes the information in the bit stream based on a coding method suchas exponential Golomb coding, CAVLC, or CABAC, and output syntaxelements required for image reconstruction and quantized values oftransform coefficients for residual. More specifically, the CABACentropy decoding method may receive a bin corresponding to each syntaxelement in the bit stream, determine a context model using a decodingtarget syntax element information, decoding information of a decodingtarget block or information of a symbol/bin decoded in a previous stage,and perform an arithmetic decoding on the bin by predicting aprobability of occurrence of a bin according to the determined contextmodel, and generate a symbol corresponding to the value of each syntaxelement. In this case, the CABAC entropy decoding method may update thecontext model by using the information of the decoded symbol/bin for acontext model of a next symbol/bin after determining the context model.The information related to the prediction among the information decodedby the entropy decoder 310 may be provided to the predictor (the interpredictor 332 and the intra predictor 331), and the residual value onwhich the entropy decoding was performed in the entropy decoder 310,that is, the quantized transform coefficients and related parameterinformation, may be input to the residual processor 320. The residualprocessor 320 may derive the residual signal (the residual block, theresidual samples, the residual sample array). In addition, informationon filtering among information decoded by the entropy decoder 310 may beprovided to the filter 350. Meanwhile, a receiver (not shown) forreceiving a signal output from the encoding apparatus may be furtherconfigured as an internal/external element of the decoding apparatus300, or the receiver may be a component of the entropy decoder 310.Meanwhile, the decoding apparatus according to the present disclosuremay be referred to as a video/image/picture decoding apparatus, and thedecoding apparatus may be classified into an information decoder(video/image/picture information decoder) and a sample decoder(video/image/picture sample decoder). The information decoder mayinclude the entropy decoder 310, and the sample decoder may include atleast one of the dequantizer 321, the inverse transformer 322, the adder340, the filter 350, the memory 360, the inter predictor 332, and theintra predictor 331.

The dequantizer 321 may dequantize the quantized transform coefficientsand output the transform coefficients. The dequantizer 321 may rearrangethe quantized transform coefficients in the form of a two-dimensionalblock form. In this case, the rearrangement may be performed based onthe coefficient scanning order performed in the encoding apparatus. Thedequantizer 321 may perform dequantization on the quantized transformcoefficients by using a quantization parameter (e.g., quantization stepsize information) and obtain transform coefficients.

The inverse transformer 322 inversely transforms the transformcoefficients to obtain a residual signal (residual block, residualsample array).

The predictor may perform prediction on the current block and generate apredicted block including prediction samples for the current block. Thepredictor may determine whether intra prediction or inter prediction isapplied to the current block based on the information on the predictionoutput from the entropy decoder 310 and may determine a specificintra/inter prediction mode.

The predictor 320 may generate a prediction signal based on variousprediction methods described below. For example, the predictor may notonly apply intra prediction or inter prediction to predict one block butalso simultaneously apply intra prediction and inter prediction. Thismay be called combined inter and intra prediction (CIIP). In addition,the predictor may be based on an intra block copy (IBC) prediction modeor a palette mode for prediction of a block. The IBC prediction mode orpalette mode may be used for content image/video coding of a game or thelike, for example, screen content coding (SCC). The IBC basicallyperforms prediction in the current picture but may be performedsimilarly to inter prediction in that a reference block is derived inthe current picture. That is, the IBC may use at least one of the interprediction techniques described in the present disclosure. The palettemode may be considered as an example of intra coding or intraprediction. When the palette mode is applied, a sample value within apicture may be signaled based on information on the palette table andthe palette index.

The intra predictor 331 may predict the current block by referring tothe samples in the current picture. The referred samples may be locatedin the neighborhood of the current block or may be located apartaccording to the prediction mode. In the intra prediction, predictionmodes may include a plurality of non-directional modes and a pluralityof directional modes. The intra predictor 331 may determine theprediction mode applied to the current block by using a prediction modeapplied to a neighboring block.

The inter predictor 332 may derive a predicted block for the currentblock based on a reference block (reference sample array) specified by amotion vector on a reference picture. In this case, in order to reducethe amount of motion information transmitted in the inter predictionmode, motion information may be predicted in units of blocks,sub-blocks, or samples based on correlation of motion informationbetween the neighboring block and the current block. The motioninformation may include a motion vector and a reference picture index.The motion information may further include inter prediction direction(L0 prediction, L1 prediction, Bi prediction, etc.) information. In thecase of inter prediction, the neighboring block may include a spatialneighboring block present in the current picture and a temporalneighboring block present in the reference picture. For example, theinter predictor 332 may configure a motion information candidate listbased on neighboring blocks and derive a motion vector of the currentblock and/or a reference picture index based on the received candidateselection information. Inter prediction may be performed based onvarious prediction modes, and the information on the prediction mayinclude information indicating a mode of inter prediction for thecurrent block.

The adder 340 may generate a reconstructed signal (reconstructedpicture, reconstructed block, reconstructed sample array) by adding theobtained residual signal to the prediction signal (predicted block,predicted sample array) output from the predictor (including the interpredictor 332 and/or the intra predictor 331). If there is no residualfor the block to be processed, such as when the skip mode is applied,the predicted block may be used as the reconstructed block.

The adder 340 may be called reconstructor or a reconstructed blockgenerator. The generated reconstructed signal may be used for intraprediction of a next block to be processed in the current picture, maybe output through filtering as described below, or may be used for interprediction of a next picture.

Meanwhile, luma mapping with chroma scaling (LMCS) may be applied in thepicture decoding process.

The filter 350 may improve subjective/objective image quality byapplying filtering to the reconstructed signal. For example, the filter350 may generate a modified reconstructed picture by applying variousfiltering methods to the reconstructed picture and store the modifiedreconstructed picture in the memory 360, specifically, a DPB of thememory 360. The various filtering methods may include, for example,deblocking filtering, a sample adaptive offset, an adaptive loop filter,a bilateral filter, and the like.

The (modified) reconstructed picture stored in the DPB of the memory 360may be used as a reference picture in the inter predictor 332. Thememory 360 may store the motion information of the block from which themotion information in the current picture is derived (or decoded) and/orthe motion information of the blocks in the picture that have alreadybeen reconstructed. The stored motion information may be transmitted tothe inter predictor 260 so as to be utilized as the motion informationof the spatial neighboring block or the motion information of thetemporal neighboring block. The memory 360 may store reconstructedsamples of reconstructed blocks in the current picture and transfer thereconstructed samples to the intra predictor 331.

In the present disclosure, the embodiments described in the filter 260,the inter predictor 221, and the intra predictor 222 of the encodingapparatus 200 may be the same as or respectively applied to correspondto the filter 350, the inter predictor 332, and the intra predictor 331of the decoding apparatus 300. The same may also apply to the unit 332and the intra predictor 331.

In the present disclosure, at least one of quantization/inversequantization and/or transform/inverse transform may be omitted. When thequantization/inverse quantization is omitted, the quantized transformcoefficients may be called transform coefficients. When thetransform/inverse transform is omitted, the transform coefficients maybe called coefficients or residual coefficients, or may still be calledtransform coefficients for uniformity of expression.

In the present disclosure, a quantized transform coefficient and atransform coefficient may be referred to as a transform coefficient anda scaled transform coefficient, respectively. In this case, the residualinformation may include information on transform coefficient(s), and theinformation on the transform coefficient(s) may be signaled throughresidual coding syntax. Transform coefficients may be derived based onthe residual information (or the information on the transformcoefficient(s)), and scaled transform coefficients may be derived byinverse transforming (scaling) on the transform coefficients. Residualsamples may be derived based on the inverse transforming (transforming)on the scaled transform coefficients. This may be applied/expressed inother parts of the present disclosure as well.

Meanwhile, as described above, in performing video coding, prediction isperformed to improve compression efficiency. Through this, a predictedblock including prediction samples for a current block as a block to becoded (i.e., a coding target block) may be generated. Here, thepredicted block includes prediction samples in a spatial domain (orpixel domain). The predicted block is derived in the same manner in anencoding apparatus and a decoding apparatus, and the encoding apparatusmay signal information (residual information) on residual between theoriginal block and the predicted block, rather than an original samplevalue of an original block, to the decoding apparatus, therebyincreasing image coding efficiency. The decoding apparatus may derive aresidual block including residual samples based on the residualinformation, add the residual block and the predicted block to generatereconstructed blocks including reconstructed samples, and generate areconstructed picture including the reconstructed blocks.

The residual information may be generated through a transform andquantization procedure. For example, the encoding apparatus may derive aresidual block between the original block and the predicted block,perform a transform procedure on residual samples (residual samplearray) included in the residual block to derive transform coefficients,perform a quantization procedure on the transform coefficients to derivequantized transform coefficients, and signal related residualinformation to the decoding apparatus (through a bit stream). Here, theresidual information may include value information of the quantizedtransform coefficients, location information, a transform technique, atransform kernel, a quantization parameter, and the like. The decodingapparatus may perform dequantization/inverse transform procedure basedon the residual information and derive residual samples (or residualblocks). The decoding apparatus may generate a reconstructed picturebased on the predicted block and the residual block. Also, for referencefor inter prediction of a picture afterward, the encoding apparatus mayalso dequantize/inverse-transform the quantized transform coefficientsto derive a residual block and generate a reconstructed picture basedthereon.

Intra prediction may refer to prediction that generates predictionsamples for a current block based on reference samples in a picture towhich the current block belongs (hereinafter, referred to as a currentpicture). When the intra prediction is applied to the current block,neighboring reference samples to be used for the intra prediction of thecurrent block may be derived. The neighboring reference samples of thecurrent block may include a sample adjacent to the left boundary of thecurrent block of size nW×nH and a total of 2×nH samples adjacent to thebottom-left of the current block, a sample adjacent to the top boundaryof the current block and a total of 2×nW samples adjacent to thetop-right and a sample adjacent to the top-left of the current block.Alternatively, the neighboring reference samples of the current blockmay include a plurality of columns of top neighboring samples and aplurality of rows of left neighboring samples. In addition, theneighboring reference samples of the current block may include a totalof nH samples adjacent to the right boundary of the current block ofsize nW×nH, a total of nW samples adjacent to the bottom boundary of thecurrent block and a sample adjacent to the bottom-right of the currentblock.

However, some of the neighboring reference samples of the current blockhave not yet been decoded or may not be available. In this case, thedecoder may construct neighboring reference samples to be used forprediction by substituting unavailable samples with available samples.Alternatively, neighboring reference samples to be used for predictionmay be configured through interpolation of available samples.

When the neighboring reference samples are derived, (i) a predictionsample may be derived based on the average or interpolation ofneighboring reference samples of the current block, or (ii) theprediction sample may be derived based on a reference sample existing ina specific (prediction) direction with respect to a prediction sampleamong the neighboring reference samples of the current block. The caseof (i) may be called a non-directional mode or a non-angular mode, andthe case of (ii) may be called a directional mode or an angular mode.

In addition, the prediction sample may be generated throughinterpolation of a first neighboring sample located in the predictiondirection of the intra prediction mode of the current block based on theprediction sample of the current block and a second neighboring samplelocated in a direction opposite to the prediction direction among theneighboring reference samples. The above-described case may be referredto as linear interpolation intra prediction (LIP). In addition, chromaprediction samples may be generated based on the luma samples using alinear model (LM). This case may be called an LM mode or a chromacomponent LM (CCLM) mode.

In addition, a temporary prediction sample of the current block isderived based on the filtered neighboring reference samples, and aprediction sample of the current block may also be derived by weightedsumming the temporary prediction sample and at least one referencesample derived according to the intra prediction mode among the existingneighboring reference samples, that is, unfiltered neighboring referencesamples. The above-described case may be referred to as positiondependent intra prediction (PDPC).

In addition, a reference sample line with the highest predictionaccuracy among neighboring multiple reference sample lines of thecurrent block is selected, and a prediction sample is derived using areference sample located in the prediction direction in the selectedline. In this case, intra prediction encoding may be performed byindicating (signaling) the used reference sample line to the decodingapparatus. The above-described case may be referred to asmulti-reference line intra prediction or MRL-based intra prediction.

In addition, the current block is divided into vertical or horizontalsub-partitions and intra prediction is performed based on the same intraprediction mode, but neighboring reference samples may be derived andused in units of the sub-partitions. That is, in this case, the intraprediction mode for the current block is equally applied to thesub-partitions, but the intra prediction performance may be improved insome cases by deriving and using the neighboring reference samples inunits of the sub-partitions. This prediction method may be calledintra-prediction based on intra sub-partitions (ISP).

The above-described intra prediction methods may be called intraprediction types to be distinguished from the intra prediction mode. Theintra prediction types may be referred to by various terms such as intraprediction technique or additional intra prediction modes. For example,the intra prediction types (or additional intra prediction modes, etc.)may include at least one of the aforementioned LIP, PDPC, MRL, and ISP.A general intra prediction method excluding a specific intra predictiontype such as LIP, PDPC, MRL, and ISP may be referred to as a normalintra prediction type. The normal intra prediction type may be generallyapplied when the above specific intra prediction type is not applied,and prediction may be performed based on the above-described intraprediction mode. Meanwhile, if necessary, post-processing filtering maybe performed on the derived prediction sample.

Specifically, the intra prediction process may include an intraprediction mode/type determination step, neighboring reference samplesderivation step, and an intra prediction mode/type based predictionsample derivation step. In addition, if necessary, a post-filtering stepmay be performed on the derived prediction sample.

FIG. 4 illustrates an example of an intra prediction-based video/imageencoding method.

Referring to FIG. 4 , the encoding device performs intra prediction onthe current block S400. The encoding device derives an intra predictionmode/type for the current block, derives neighboring reference samplesof the current block, generates prediction samples in the current blockbased on the intra prediction mode/type and the neighboring referencesamples. Here, the intra prediction mode/type determination, neighboringreference samples derivation, and prediction samples generationprocedures may be performed simultaneously, or one procedure may beperformed before another procedure. The encoding device may determine amode/type applied to the current block from among a plurality of intraprediction modes/types. The encoding device may compare RD costs for theintra prediction mode/types and determine an optimal intra predictionmode/type for the current block.

Meanwhile, the encoding device may perform a prediction sample filteringprocedure. The prediction sample filtering may be referred to as postfiltering. Some or all of the prediction samples may be filtered by theprediction sample filtering procedure. In some cases, the predictionsample filtering procedure may be omitted.

The encoding device generates residual samples for the current blockbased on the (filtered) prediction samples S410. The encoding device maycompare the prediction samples in the original samples of the currentblock based on the phase and derive the residual samples.

The encoding device may encode image information including informationon the intra prediction (prediction information) and residualinformation on the residual samples S420. The prediction information mayinclude the intra prediction mode information and the intra predictiontype information. The encoding device may output encoded imageinformation in the form of a bitstream. The output bitstream may betransmitted to the decoding device through a storage medium or anetwork.

The residual information may include residual coding syntax, which willbe described later. The encoding device may transform/quantize theresidual samples to derive quantized transform coefficients. Theresidual information may include information on the quantized transformcoefficients.

Meanwhile, as described above, the encoding device may generate areconstructed picture (including reconstructed samples and reconstructedblocks). To this end, the encoding device may derive (modified) residualsamples by performing inverse quantization/inverse transformation on thequantized transform coefficients again. The reason for performing theinverse quantization/inverse transformation again aftertransforming/quantizing the residual samples in this way is to derivethe same residual samples as the residual samples derived in thedecoding device as described above. The encoding device may generate areconstructed block including reconstructed samples for the currentblock based on the prediction samples and the (modified) residualsamples. A reconstructed picture for the current picture may begenerated based on the reconstructed block. As described above, anin-loop filtering procedure may be further applied to the reconstructedpicture.

FIG. 5 illustrates an example of an intra prediction-based video/imagedecoding method.

The decoding device may perform an operation corresponding to theoperation performed by the encoding apparatus.

Prediction information and residual information may be obtained from abitstream. Residual samples for the current block may be derived basedon the residual information. Specifically, transform coefficients may bederived by performing inverse quantization based on the quantizedtransform coefficients derived based on the residual information,residual samples for the current block may be derived by performinginverse transform on the transform coefficients.

Specifically, the decoding device may derive the intra predictionmode/type for the current block based on the received predictioninformation (intra prediction mode/type information) S500. The decodingdevice may derive neighboring reference samples of the current blockS510. The decoding device generates prediction samples in the currentblock based on the intra prediction mode/type and the neighboringreference samples S520. In this case, the decoding device may perform aprediction sample filtering procedure. The Predictive sample filteringmay be referred to as post filtering. Some or all of the predictionsamples may be filtered by the prediction sample filtering procedure. Insome cases, the prediction sample filtering procedure may be omitted.

The decoding device generates residual samples for the current blockbased on the received residual information S530. The decoding device maygenerate reconstructed samples for the current block based on theprediction samples and the residual samples, and may derive areconstructed block including the reconstructed samples S540. Areconstructed picture for the current picture may be generated based onthe reconstructed block. As described above, an in-loop filteringprocedure may be further applied to the reconstructed picture.

The intra prediction mode information may include, for example, flaginformation (ex. intra_luma_mpm_flag) indicating whether MPM (mostprobable mode) is applied to the current block or whether a remainingmode is applied, and, when the MPM is applied to the current block, theprediction mode information may further include index information (eg,intra_luma_mpm_idx) indicating one of the intra prediction modecandidates (MPM candidates). The intra prediction mode candidates (MPMcandidates) may be constructed of an MPM candidate list or an MPM list.In addition, when the MPM is not applied to the current block, the intraprediction mode information includes remaining mode information (ex.intra_luma_mpm_remainder) indicating one of the remaining intraprediction modes except for the intra prediction mode candidates (MPMcandidates). The decoding device may determine the intra prediction modeof the current block based on the intra prediction mode information.

Also, the intra prediction type information may be implemented invarious forms. For example, the intra prediction type information mayinclude intra prediction type index information indicating one of theintra prediction types. As another example, the intra prediction typeinformation may include at least one of reference sample lineinformation (ex. intra_luma_ref_idx) representing whether the MRL isapplied to the current block and, if applied, which reference sampleline is used, ISP flag information representing whether the ISP isapplied to the current block (ex. intra_subpartitions_mode_flag), ISPtype information indicating a split type of subpartitions when the ISPis applied (ex. intra_subpartitions_split_flag), flag informationrepresenting whether the PDPC is applied or flag informationrepresenting whether the LIP is applied. Also, the intra prediction typeinformation may include a MIP flag representing whether matrix-basedintra prediction (MIP) is applied to the current block.

The intra prediction mode information and/or the intra prediction typeinformation may be encoded/decoded through a coding method described inthe present disclosure. For example, the intra prediction modeinformation and/or the intra prediction type information may beencoded/decoded through entropy coding (e.g., CABAC, CAVLC).

FIG. 6 schematically shows an intra prediction procedure.

Referring to FIG. 6 , as described above, the intra prediction proceduremay include a step of determinating an intra prediction mode/type, astep of deriving neighboring reference samples, and a step of performingintra prediction (generating a prediction sample). The intra predictionprocedure may be performed by the encoding device and the decodingdevice as described above. In the present disclosure, a coding devicemay include the encoding device and/or the decoding device.

Referring to FIG. 6 , the coding device determines an intra predictionmode/type S600.

The encoding device may determine an intra prediction mode/type appliedto the current block from among the various intra prediction modes/typesdescribed above, and may generate prediction related information. Theprediction related information may include intra prediction modeinformation representing an intra prediction mode applied to the currentblock and/or intra prediction type information representing an intraprediction type applied to the current block. The decoding device maydetermine an intra prediction mode/type applied to the current blockbased on the prediction related information.

The intra prediction mode information may include, for example, flaginformation (ex. intra_luma_mpm_flag) representing whether a mostprobable mode (MPM) is applied to the current block or a remaining modeis applied, and the When the MPM is applied to the current block, theprediction mode information may further include index information (eg,intra_luma_mpm_idx) indicating one of the intra prediction modecandidates (MPM candidates). The intra prediction mode candidates (MPMcandidates) may be constructed of an MPM candidate list or an MPM list.In addition, when the MPM is not applied to the current block, the intraprediction mode information may further include remaining modeinformation (ex. intra_luma_mpm_remainder) indicating one of theremaining intra prediction modes except for the intra prediction modecandidates (MPM candidates). The decoding device may determine the intraprediction mode of the current block based on the intra prediction modeinformation.

In addition, the intra prediction type information may be implemented invarious forms. For example, the intra prediction type information mayinclude intra prediction type index information indicating one of theintra prediction types. As another example, the intra prediction typeinformation may include at least one of reference sample lineinformation (ex. intra_luma_ref_idx) representing whether the MRL isapplied to the current block and, if applied, which reference sampleline is used, ISP flag information representing whether the ISP isapplied to the current block (ex. intra_subpartitions_mode_flag), ISPtype information indicating a split type of subpartitions when the ISPis applied (ex. intra_subpartitions_split_flag), flag informationrepresenting whether the PDPC is applied or flag informationrepresenting whether the LIP is applied. Also, the intra prediction typeinformation may include a MIP flag representing whether matrix-basedintra prediction (MIP) is applied to the current block.

For example, when intra prediction is applied, an intra prediction modeapplied to the current block may be determined using an intra predictionmode of a neighboring block. For example, the coding device may selectone of most probable mode (MPM) candidates in the MPM list derived basedon additional candidate modes and/or an intra prediction mode of theneighboring block (eg, the left and/or top neighboring block) of thecurrent block, or select one of the remaining intra prediction modes notincluded in the MPM candidates (and planar mode) based on the MPMremainder information (remaining intra prediction mode information). TheMPM list may be configured to include or not include the planner mode asa candidate. For example, when the MPM list includes a planner mode as acandidate, the MPM list may have 6 candidates, and when the MPM listdoes not include a planner mode as a candidate, the MPM list may have 5candidates. When the MPM list does not include the planar mode as acandidate, a not planar flag (ex. intra_luma_not_planar_flag)representing whether the intra prediction mode of the current block isnot the planar mode may be signaled. For example, the MPM flag may besignaled first, and the MPM index and not planner flag may be signaledwhen the value of the MPM flag is 1. Also, the MPM index may be signaledwhen the value of the not planner flag is 1. Here, the fact that the MPMlist is configured not to include the planner mode as a candidate isthat the planner mode is always considered as MPM rather than that theplanner mode is not MPM, thus, the flag (not planar flag) is signaledfirst to check whether it is the planar mode.

For example, whether the intra prediction mode applied to the currentblock is among the MPM candidates (and the planar mode) or the remainingmodes may be indicated based on the MPM flag (eg, intra_luma_mpm_flag).The MPM flag with a value of 1 may indicate that the intra predictionmode for the current block is within MPM candidates (and planar mode),and The MPM flag with a value of 0 may indicate that the intraprediction mode for the current block is not within MPM candidates (andplanar mode). The not planar flag (ex. intra_luma_not_planar_flag) witha value of 0 may indicate that the intra prediction mode for the currentblock is a planar mode, and the not planar flag with a value of 1 mayindicate that the intra prediction mode for the current block is not theplanar mode. The MPM index may be signaled in the form of an mpm_idx orintra_luma_mpm_idx syntax element, and the remaining intra predictionmode information may be signaled in the form of arem_intra_luma_pred_mode or intra_luma_mpm_remainder syntax element. Forexample, the remaining intra prediction mode information may indicateone of the remaining intra prediction modes not included in the MPMcandidates (and planar mode) among all intra prediction modes byindexing in the order of prediction mode number. The intra predictionmode may be an intra prediction mode for a luma component (sample).Hereinafter, the intra prediction mode information may include at leastone of the MPM flag (ex. intra_luma_mpm_flag), the not planar flag (ex.intra_luma_not_planar_flag), the MPM index (ex. mpm_idx orintra_luma_mpm_idx), or the remaining intra prediction mode information(rem_intra_luma_luma_mpm_mode or intra_luma_mpminder). In the presentdisclosure, the MPM list may be referred to by various terms such as anMPM candidate list and candModeList.

When the MIP is applied to the current block, a separate mpm flag (ex.intra_mip_mpm_flag) for the MIP, an mpm index (ex. intra_mip_mpm_idx),and remaining intra prediction mode information (ex.intra_mip_mpm_remainder) may be signaled, and the not planar flag maynot be signaled.

In other words, in general, when a block partition for an image isperformed, the current block to be coded and a neighboring block havesimilar image characteristics. Therefore, there is a high probabilitythat the current block and the neighboring block have the same orsimilar intra prediction mode. Accordingly, the encoder may use theintra prediction mode of the neighboring block to encode the intraprediction mode of the current block.

The coding device may construct a most probable modes (MPM) list for thecurrent block. The MPM list may be referred to as the MPM candidatelist. Here, the MPM may refer to modes used to improve coding efficiencyin consideration of the similarity between the current block and theneighboring blocks during intra prediction mode coding. As describedabove, the MPM list may be constructed to include the planar mode, ormay be constructed to exclude the planar mode. For example, when the MPMlist includes the planar mode, the number of candidates in the MPM listmay be 6. And, when the MPM list does not include the planar mode, thenumber of candidates in the MPM list may be 5.

The encoding device may perform prediction based on various intraprediction modes, and may determine an optimal intra prediction modebased on rate-distortion optimization (RDO) based thereon. In this case,the encoding device may determine the optimal intra prediction mode byusing only the MPM candidates and planar mode configured in the MPMlist, or by further using the remaining intra prediction modes as wellas the MPM candidates and planar mode configured in the MPM list.Specifically, for example, if the intra prediction type of the currentblock is a specific type (ex. LIP, MRL, or ISP) other than the normalintra prediction type, the encoding device may determine the optimalintra prediction mode by considering only the MPM candidates and theplanar mode as intra prediction mode candidates for the current block.That is, in this case, the intra prediction mode for the current blockmay be determined only from among the MPM candidates and the planarmode, and in this case, encoding/signaling of the mpm flag may not beperformed. In this case, the decoding device may infer that the mpm flagis 1 without separately signaling the mpm flag.

Meanwhile, in general, when the intra prediction mode of the currentblock is not the planar mode and is one of the MPM candidates in the MPMlist, the encoding device generates an mpm index (mpm idx) indicatingone of the MPM candidates. when the intra prediction mode of the currentblock is not included in the MPM list, the encoding device generates MPMreminder information (remaining intra prediction mode information)indicating the same mode as the intra prediction mode of the currentblock among the remaining intra prediction modes not included in the MPMlist (and planar mode). The MPM reminder information may include, forexample, an intra_luma_mpm_remainder syntax element.

The decoding device obtains intra prediction mode information from thebitstream. As described above, the intra prediction mode information mayinclude at least one of an MPM flag, a not planner flag, an MPM index,and MPM remaster information (remaining intra prediction modeinformation). The decoding device may construct the MPM list. The MPMlist is constructed the same as the MPM list constructed in the encodingdevice. That is, the MPM list may include intra prediction modes ofneighboring blocks, or may further include specific intra predictionmodes according to a predetermined method.

The decoding device may determine the intra prediction mode of thecurrent block based on the MPM list and the intra prediction modeinformation. For example, when the value of the MPM flag is 1, thedecoding device may derive the planar mode as the intra prediction modeof the current block (based on not planar flag) or derive the candidateindicated by the MPM index from among the MPM candidates in the MPM listas the intra prediction mode of the current block. Here, the MPMcandidates may represent only candidates included in the MPM list, ormay include not only candidates included in the MPM list but also theplanar mode applicable when the value of the MPM flag is 1.

As another example, when the value of the MPM flag is 0, the decodingdevice may derive an intra prediction mode indicated by the remainingintra prediction mode information (which may be referred to as mpmremainder information) among the remaining intra prediction modes notincluded in the MPM list and the planner mode as the intra predictionmode of the current block. Meanwhile, as another example, when the intraprediction type of the current block is a specific type (ex. LIP, MRL orISP, etc.), the decoding device may derive a candidate indicated by theMPM flag in the planar mode or the MPM list as the intra prediction modeof the current block without parsing/decoding/checking the MPM flag.

The coding device derives neighboring reference samples of the currentblock S610. When intra prediction is applied to the current block, theneighboring reference samples to be used for the intra prediction of thecurrent block may be derived. The neighboring reference samples of thecurrent block may include a sample adjacent to the left boundary of thecurrent block of size nW×nH and a total of 2×nH samples adjacent to thebottom-left of the current block, a sample adjacent to the top boundaryof the current block and a total of 2×nW samples adjacent to thetop-right and a sample adjacent to the top-left of the current block.Alternatively, the neighboring reference samples of the current blockmay include a plurality of columns of top neighboring samples and aplurality of rows of left neighboring samples. In addition, theneighboring reference samples of the current block may include a totalof nH samples adjacent to the right boundary of the current block ofsize nW×nH, a total of nW samples adjacent to the bottom boundary of thecurrent block and a sample adjacent to the bottom-right of the currentblock.

On the other hand, when the MRL is applied (that is, when the value ofthe MRL index is greater than 0), the neighboring reference samples maybe located on lines 1 to 2 instead of line 0 adjacent to the currentblock on the left/top side, and in this case, the number of theneighboring reference samples may be further increased. Meanwhile, whenthe ISP is applied, the neighboring reference samples may be derived inunits of sub-partitions.

The coding device derives prediction samples by performing intraprediction on the current block S620. The coding device may derive theprediction samples based on the intra prediction mode/type and theneighboring samples. The coding device may derive a reference sampleaccording to an intra prediction mode of the current block amongneighboring reference samples of the current block, and may derive aprediction sample of the current block based on the reference sample.

Meanwhile, when inter prediction is applied, the predictor of theencoding apparatus/decoding apparatus may derive prediction samples byperforming inter prediction in units of blocks. The inter prediction maybe applied when performing the prediction on the current block. That is,the predictor (more specifically, inter predictor) of theencoding/decoding apparatus may derive prediction samples by performingthe inter prediction in units of the block. The inter prediction mayrepresent prediction derived by a method dependent to the data elements(e.g., sample values or motion information) of a picture(s) other thanthe current picture. When the inter prediction is applied to the currentblock, a predicted block (prediction sample array) for the current blockmay be derived based on a reference block (reference sample array)specified by the motion vector on the reference picture indicated by thereference picture index. In this case, in order to reduce an amount ofmotion information transmitted in the inter-prediction mode, the motioninformation of the current block may be predicted in units of a block, asubblock, or a sample based on a correlation of the motion informationbetween the neighboring block and the current block. The motioninformation may include the motion vector and the reference pictureindex. The motion information may further include inter-prediction type(L0 prediction, L1 prediction, Bi prediction, etc.) information. In thecase of applying the inter prediction, the neighboring block may includea spatial neighboring block which is present in the current picture anda temporal neighboring block which is present in the reference picture.A reference picture including the reference block and a referencepicture including the temporal neighboring block may be the same as eachother or different from each other. The temporal neighboring block maybe referred to as a name such as a collocated reference block, acollocated CU (colCU), etc., and the reference picture including thetemporal neighboring block may be referred to as a collocated picture(colPic). For example, a motion information candidate list may beconfigured based on the neighboring blocks of the current block and aflag or index information indicating which candidate is selected (used)may be signaled in order to derive the motion vector and/or referencepicture index of the current block. The inter prediction may beperformed based on various prediction modes and for example, in the caseof a skip mode and a merge mode, the motion information of the currentblock may be the same as the motion information of the selectedneighboring block. In the case of the skip mode, the residual signal maynot be transmitted unlike the merge mode. In the case of a motion vectorprediction (MVP) mode, the motion vector of the selected neighboringblock may be used as a motion vector predictor and a motion vectordifference may be signaled. In this case, the motion vector of thecurrent block may be derived by using a sum of the motion vectorpredictor and the motion vector difference.

The motion information may further include L0 motion information and/orL1 motion information according to the inter-prediction type (L0prediction, L1 prediction, Bi prediction, etc.). A L0-direction motionvector may be referred to as an L0 motion vector or MVL0 and anL1-direction motion vector may be referred to as an L1 motion vector orMVL1. A prediction based on the L0 motion vector may be referred to asan L0 prediction, a prediction based on the L1 motion vector may bereferred to as an L1 prediction, and a prediction based on both the L0motion vector and the L1 motion vector may be referred to as abi-prediction. Here, the L0 motion vector may indicate a motion vectorassociated with a reference picture list L0 and the L1 motion vector mayindicate a motion vector associated with a reference picture list L1.The reference picture list L0 may include pictures prior to the currentpicture in an output order and the reference picture list L1 may includepictures subsequent to the current picture in the output order, as thereference pictures. The prior pictures may be referred to as a forward(reference) picture and the subsequent pictures may be referred to as areverse (reference) picture. The reference picture list L0 may furtherinclude the pictures subsequent to the current picture in the outputorder as the reference pictures. In this case, the prior pictures may befirst indexed in the reference picture list L0 and the subsequentpictures may then be indexed. The reference picture list L1 may furtherinclude the pictures prior to the current picture in the output order asthe reference pictures. In this case, the subsequent pictures may befirst indexed in the reference picture list L1 and the prior picturesmay then be indexed. Here, the output order may correspond to a pictureorder count (POC) order.

A video/image encoding process based on inter prediction mayschematically include, for example, the following.

FIG. 7 illustrates an example of an inter prediction-based video/imageencoding method.

The encoding apparatus performs the inter prediction for the currentblock (S700). The encoding apparatus may derive the inter predictionmode and the motion information of the current block and generate theprediction samples of the current block. Here, an inter prediction modedetermining process, a motion information deriving process, and ageneration process of the prediction samples may be simultaneouslyperformed and any one process may be performed earlier than otherprocess. For example, the inter-prediction unit of the encodingapparatus may include a prediction mode determination unit, a motioninformation derivation unit, and a prediction sample derivation unit,and the prediction mode determination unit may determine the predictionmode for the current block, the motion information derivation unit mayderive the motion information of the current block, and the predictionsample derivation unit may derive the prediction samples of the currentblock. For example, the inter-prediction unit of the encoding apparatusmay search a block similar to the current block in a predetermined area(search area) of reference pictures through motion estimation and derivea reference block in which a difference from the current block isminimum or is equal to or less than a predetermined criterion. Areference picture index indicating a reference picture at which thereference block is positioned may be derived based thereon and a motionvector may be derived based on a difference in location between thereference block and the current block. The encoding apparatus maydetermine a mode applied to the current block among various predictionmodes. The encoding apparatus may compare RD cost for the variousprediction modes and determine an optimal prediction mode for thecurrent block.

For example, when the skip mode or the merge mode is applied to thecurrent block, the encoding apparatus may configure a merging candidatelist to be described below and derive a reference block in which adifference from the current block is minimum or is equal to or less thana predetermined criterion among reference blocks indicated by mergecandidates included in the merging candidate list. In this case, a mergecandidate associated with the derived reference block may be selectedand merge index information indicating the selected merge candidate maybe generated and signaled to the decoding apparatus. The motioninformation of the current block may be derived by using the motioninformation of the selected merge candidate.

As another example, when an (A)MVP mode is applied to the current block,the encoding apparatus may configure an (A)MVP candidate list to bedescribed below and use a motion vector of a selected mvp candidateamong motion vector predictor (mvp) candidates included in the (A)MVPcandidate list as the mvp of the current block. In this case, forexample, the motion vector indicating the reference block derived by themotion estimation may be used as the motion vector of the current blockand an mvp candidate having a motion vector with a smallest differencefrom the motion vector of the current block among the mvp candidates maybecome the selected mvp candidate. A motion vector difference (MVD)which is a difference obtained by subtracting the mvp from the motionvector of the current block may be derived. In this case, theinformation on the MVD may be signaled to the decoding apparatus.Further, when the (A)MVP mode is applied, the value of the referencepicture index may be configured as reference picture index informationand separately signaled to the decoding apparatus.

The encoding apparatus may derive the residual samples based on thepredicted samples (S710). The encoding apparatus may derive the residualsamples by comparing original samples and the prediction samples of thecurrent block.

The encoding apparatus encodes image information including predictioninformation and residual information (S720). The encoding apparatus mayoutput the encoded image information in the form of a bitstream. Theprediction information may include information on prediction modeinformation (e.g., skip flag, merge flag or mode index, etc.) andinformation on motion information as information related to theprediction procedure. The information on the motion information mayinclude candidate selection information (e.g., merge index, mvp flag ormvp index) which is information for deriving the motion vector. Further,the information on the motion information may include the information onthe MVD and/or the reference picture index information. Further, theinformation on the motion information may include information indicatingwhether to apply the L0 prediction, the L1 prediction, or thebi-prediction. The residual information is information on the residualsamples. The residual information may include information on quantizedtransform coefficients for the residual samples.

An output bitstream may be stored in a (digital) storage medium andtransferred to the decoding apparatus or transferred to the decodingapparatus via the network.

Meanwhile, as described above, the encoding apparatus may generate areconstructed picture (including reconstructed samples and reconstructedblocks) based on the reference samples and the residual samples. This isto derive the same prediction result as that performed by the decodingapparatus, and as a result, coding efficiency may be increased.Accordingly, the encoding apparatus may store the reconstruction picture(or reconstruction samples or reconstruction blocks) in the memory andutilize the reconstruction picture as the reference picture. The in-loopfiltering process may be further applied to the reconstruction pictureas described above.

A video/image decoding process based on inter prediction mayschematically include, for example, the following.

FIG. 8 illustrates an example of an inter prediction-based video/imagedecoding method.

Referring to FIG. 8 , the decoding apparatus may perform an operationcorresponding to the operation performed by the encoding apparatus. Thedecoding apparatus may perform the prediction for the current blockbased on received prediction information and derive the predictionsamples.

Specifically, the decoding apparatus may determine the prediction modefor the current block based on the received prediction information(S800). The decoding apparatus may determine which inter prediction modeis applied to the current block based on the prediction mode informationin the prediction information.

For example, it may be determined whether the merge mode or the (A)MVPmode is applied to the current block based on the merge flag.Alternatively, one of various inter prediction mode candidates may beselected based on the mode index. The inter prediction mode candidatesmay include a skip mode, a merge mode, and/or an (A)MVP mode or mayinclude various inter prediction modes to be described below.

The decoding apparatus derives the motion information of the currentblock based on the determined inter prediction mode (S810). For example,when the skip mode or the merge mode is applied to the current block,the decoding apparatus may configure the merge candidate list to bedescribed below and select one merge candidate among the mergecandidates included in the merge candidate list. Here, the selection maybe performed based on the selection information (merge index). Themotion information of the current block may be derived by using themotion information of the selected merge candidate. The motioninformation of the selected merge candidate may be used as the motioninformation of the current block.

As another example, when an (A)MVP mode is applied to the current block,the decoding apparatus may configure an (A)MVP candidate list to bedescribed below and use a motion vector of a selected mvp candidateamong motion vector predictor (mvp) candidates included in the (A)MVPcandidate list as the mvp of the current block. Here, the selection maybe performed based on the selection information (mvp flag or mvp index).In this case, the MVD of the current block may be derived based on theinformation on the MVD, and the motion vector of the current block maybe derived based on the mvp of the current block and the MVD. Further,the reference picture index of the current block may be derived based onthe reference picture index information. The picture indicated by thereference picture index in the reference picture list for the currentblock may be derived as the reference picture referred for the interprediction of the current block.

Meanwhile, as described below, the motion information of the currentblock may be derived without a candidate list configuration and in thiscase, the motion information of the current block may be derivedaccording to a procedure disclosed in the prediction mode. In this case,the candidate list configuration may be omitted.

The decoding apparatus may generate the prediction samples for thecurrent block based on the motion information of the current block(S820). In this case, the reference picture may be derived based on thereference picture index of the current block and the prediction samplesof the current block may be derived by using the samples of thereference block indicated by the motion vector of the current block onthe reference picture. In this case, in some cases, a predicted samplefiltering procedure for all or some of the prediction samples of thecurrent block may be further performed.

For example, the inter-prediction unit of the decoding apparatus mayinclude a prediction mode determination unit, a motion informationderivation unit, and a prediction sample derivation unit, and theprediction mode determination unit may determine the prediction mode forthe current block based on the received prediction mode information, themotion information derivation unit may derive the motion information(the motion vector and/or reference picture index) of the current blockbased on the information on the received motion information, and theprediction sample derivation unit may derive the predicted samples ofthe current block.

The decoding apparatus generates the residual samples for the currentblock based on the received residual information (S830). The decodingapparatus may generate the reconstruction samples for the current blockbased on the prediction samples and the residual samples and generatethe reconstruction picture based on the generated reconstruction samples(S840). Thereafter, the in-loop filtering procedure may be furtherapplied to the reconstruction picture as described above.

FIG. 9 schematically shows an inter prediction procedure.

Referring to FIG. 9 , as described above, the inter prediction processmay include an inter prediction mode determination step, a motioninformation derivation step according to the determined prediction mode,and a prediction processing (prediction sample generation) step based onthe derived motion information. The inter prediction process may beperformed by the encoding apparatus and the decoding apparatus asdescribed above. In this document, a coding device may include theencoding apparatus and/or the decoding apparatus.

Referring to FIG. 9 , the coding apparatus determines an interprediction mode for the current block (S900). Various inter predictionmodes may be used for the prediction of the current block in thepicture. For example, various modes, such as a merge mode, a skip mode,a motion vector prediction (MVP) mode, an affine mode, a subblock mergemode, a merge with MVD (MMVD) mode, and a historical motion vectorprediction (HMVP) mode may be used. A decoder side motion vectorrefinement (DMVR) mode, an adaptive motion vector resolution (AMVR)mode, a bi-prediction with CU-level weight (BCW), a bi-directionaloptical flow (BDOF), and the like may be further used as additionalmodes. The affine mode may also be referred to as an affine motionprediction mode. The MVP mode may also be referred to as an advancedmotion vector prediction (AMVP) mode. In the present document, somemodes and/or motion information candidates derived by some modes mayalso be included in one of motion information-related candidates inother modes. For example, the HMVP candidate may be added to the mergecandidate of the merge/skip modes, or also be added to an mvp candidateof the MVP mode. If the HMVP candidate is used as the motion informationcandidate of the merge mode or the skip mode, the HMVP candidate may bereferred to as the HMVP merge candidate.

The prediction mode information indicating the inter prediction mode ofthe current block may be signaled from the encoding apparatus to thedecoding apparatus. In this case, the prediction mode information may beincluded in the bitstream and received by the decoding apparatus. Theprediction mode information may include index information indicating oneof multiple candidate modes. Alternatively, the inter prediction modemay be indicated through a hierarchical signaling of flag information.In this case, the prediction mode information may include one or moreflags. For example, whether to apply the skip mode may be indicated bysignaling a skip flag, whether to apply the merge mode may be indicatedby signaling a merge flag when the skip mode is not applied, and it isindicated that the MVP mode is applied or a flag for additionaldistinguishing may be further signaled when the merge mode is notapplied. The affine mode may be signaled as an independent mode orsignaled as a dependent mode on the merge mode or the MVP mode. Forexample, the affine mode may include an affine merge mode and an affineMVP mode.

The coding apparatus derives motion information for the current block(S910). Motion information derivation may be derived based on the interprediction mode.

The coding apparatus may perform inter prediction using motioninformation of the current block. The encoding apparatus may deriveoptimal motion information for the current block through a motionestimation procedure. For example, the encoding apparatus may search asimilar reference block having a high correlation in units of afractional pixel within a predetermined search range in the referencepicture by using an original block in an original picture for thecurrent block and derive the motion information through the searchedreference block. The similarity of the block may be derived based on adifference of phase based sample values. For example, the similarity ofthe block may be calculated based on a sum of absolute differences (SAD)between the current block (or a template of the current block) and thereference block (or the template of the reference block). In this case,the motion information may be derived based on a reference block havinga smallest SAD in a search area. The derived motion information may besignaled to the decoding apparatus according to various methods based onthe inter prediction mode.

The coding apparatus performs inter prediction based on motioninformation for the current block (S920). The coding apparatus mayderive prediction sample(s) for the current block based on the motioninformation. A current block including prediction samples may bereferred to as a predicted block.

Meanwhile, as described above, the encoding apparatus may performvarious encoding methods such as exponential Golomb, context-adaptivevariable length coding (CAVLC), and context-adaptive binary arithmeticcoding (CABAC). In addition, the decoding apparatus may decodeinformation in a bitstream based on a coding method such as exponentialGolomb coding, CAVLC or CABAC, and output a value of a syntax elementrequired for image reconstruction and quantized values of transformcoefficients related to residuals.

For example, the coding methods described above may be performed asdescribed below.

FIG. 10 exemplarily shows context-adaptive binary arithmetic coding(CABAC) for encoding a syntax element. For example, in the CABACencoding process, when an input signal is a syntax element, rather thana binary value, the encoding apparatus may convert the input signal intoa binary value by binarizing the value of the input signal. In addition,when the input signal is already a binary value (i.e., when the value ofthe input signal is a binary value), binarization may not be performedand may be bypassed. Here, each binary number 0 or 1 constituting abinary value may be referred to as a bin. For example, if a binarystring after binarization is 110, each of 1, 1, and 0 is called one bin.The bin(s) for one syntax element may indicate a value of the syntaxelement.

Thereafter, the binarized bins of the syntax element may be input to aregular coding engine or a bypass coding engine. The regular codingengine of the encoding apparatus may allocate a context model reflectinga probability value to the corresponding bin, and may encode thecorresponding bin based on the allocated context model. The regularcoding engine of the encoding apparatus may update a context model foreach bin after performing encoding on each bin. A bin encoded asdescribed above may be referred to as a context-coded bin.

Meanwhile, when the binarized bins of the syntax element are input tothe bypass coding engine, they may be coded as follows. For example, thebypass coding engine of the encoding apparatus omits a procedure ofestimating a probability with respect to an input bin and a procedure ofupdating a probability model applied to the bin after encoding. Whenbypass encoding is applied, the encoding apparatus may encode the inputbin by applying a uniform probability distribution instead of allocatinga context model, thereby improving an encoding rate. The bin encoded asdescribed above may be referred to as a bypass bin.

Entropy decoding may represent a process of performing the same processas the entropy encoding described above in reverse order.

For example, when a syntax element is decoded based on a context model,the decoding apparatus may receive a bin corresponding to the syntaxelement through a bitstream, determine a context model using the syntaxelement and decoding information of a decoding target block or aneighbor block or information of a symbol/bin decoded in a previousstage, predict an occurrence probability of the received bin accordingto the determined context model, and perform an arithmetic decoding onthe bin to derive a value of the syntax element. Thereafter, a contextmodel of a bin which is decoded next may be updated with the determinedcontext model.

Also, for example, when a syntax element is bypass-decoded, the decodingapparatus may receive a bin corresponding to the syntax element througha bitstream, and decode the input bin by applying a uniform probabilitydistribution. In this case, the procedure of the decoding apparatus forderiving the context model of the syntax element and the procedure ofupdating the context model applied to the bin after decoding may beomitted.

As described above, residual samples may be derived as quantizedtransform coefficients through transform and quantization processes. Thequantized transform coefficients may also be referred to as transformcoefficients. In this case, the transform coefficients in a block may besignaled in the form of residual information. The residual informationmay include a residual coding syntax. That is, the encoding apparatusmay configure a residual coding syntax with residual information, encodethe same, and output it in the form of a bitstream, and the decodingapparatus may decode the residual coding syntax from the bitstream andderive residual (quantized) transform coefficients. The residual codingsyntax may include syntax elements representing whether transform wasapplied to the corresponding block, a location of a last effectivetransform coefficient in the block, whether an effective transformcoefficient exists in the subblock, a size/sign of the effectivetransform coefficient, and the like, as will be described later.

For example, syntax elements related to residual data encoding/decodingmay be represented as shown in the following table.

TABLE 1 Descriptor transform_unit( x0, y0, tbWidth, tbHeight, treeType,subTuIndex, chType ) {  if( IntraSubPartitionsSplitType != ISP_NO_SPLIT&&    treeType = = SINGLE_TREE && subTuIndex = = NumIntraSubPartiti ons− 1) {   xC = CbPosX[ chType ][ x0 ][ y0 ]   yC = CbPosY[ chType ][ x0][ y0 ]   wC = CbWidth[ chType ][ x0 ][ y0 ] / SubWidthC   hC =CbHeight[ chType ][ x0 ][ y0 ] / SubHeightC  } else {   xC = x0   yC =y0   wC = tbWidth / SubWidthC   hC = tbHeight / SubHeightC  } chromaAvailable = treeType != DUAL _TREE_LUMA && sps_chroma_form at_idc!= 0 &&   ( IntraSubPartitionsSplitType = = ISP_NO_SPLIT | |   (IntraSubPartitionsSplitType != ISP_NO_SPLIT &&   subTuIndex = =NumIntraSubPartitions − 1 ) )  if( ( treeType = = SINGLE_TREE | |treeType = = DUAL_TREE_CHROM A ) &&    sps_chroma_format_idc != 0 &&   ( ( IntraSubPartitionsSplitType = = ISP_NO_SPLIT && !( cu_sbt_flag &&   ( ( subTuIndex = = 0 && cu_sbt_pos_flag ) | |    ( subTuIndex = = 1&& !cu_sbt_pos_flag ) ) ) ) | |    ( IntraSubPartitionsSplitType !=ISP_NO_SPLIT &&    ( subTuIndex = = NumIntraSubPartitions − 1 ) ) ) ) {  tu_cb_coded_flag[ xC ][ yC ] ae(v)   tu_cr_coded_flag[ xC ][ yC ]ae(v)  }  if( treeType = = SINGLE_TREE | | treeType = = DUAL_TREE_LUMA ){   if( ( IntraSubPartitionsSplitType = = ISP_NO_SPLIT && !( cu_sbt_flag& &     ( ( subTuIndex = = 0 && cu_sbt_pos_flag ) | |     ( subTuIndex == 1 && !cu_sbt_pos_flag ) ) ) &&     ( ( CuPredMode[ chType ][ x0 ][ y0] = = MODES_INTRA &&     !cu_act_enabled_flag[ x0 ][ y0 ] ) | |     (chromaAvailable && ( tu_cb_coded_flag[ xC ][ yC ] | |    tu_cr_coded_flag[ xC ][ yC ] ) ) | |     CbWidth[ chType ][ x0 ][ y0] > MaxTbSizeY | |     CbHeight[ chType ][ x0 ][ y0 ] > MaxTbSizeY ) ) ||     ( IntraSubPartitionsSplitType != ISP_NO_SPLIT &&     ( subTuIndex< NumIntraSubPartitions − 1 | | !InferTuCbfLuma ) ) )   tu_y_coded_flag[ x0 ][ y0 ] ae(v)   if(IntraSubPartitionsSplitType !=ISP_NO_SPLIT )    InferTuCbfLuma = InferTuCbfLuma && !tu_y_coded_flag[x0 ][ y0 ]  }  if( ( CbWidth[ chType ][ x0 ][ y0 ] > 64 | | CbHeight[chType ][ x0 ][ y 0 ] > 64 | |    tu_y_coded_flag[ x0 ][ y0 ] | | (chromaAvailable && ( tu_cb_coded_flag [ xC ][ yC ] | |   tu_cr_coded_flag[ xC ][ yC ] ) ) && treeType != DUAL_TREE_CHRO MA &&   pps_cu_qp_delta_enabled_flag && !IsCuQpDeltaCoded ) {  cu_qp_delta_abs ae(v)   if( cu_qp_delta_abs )    cu_qp_delta_sign_flagae(v)  }  if( ( CbWidth[ chType ][ x0 ][ y0 ] > 64 | | CbHeight[ chType][ x0 ][ y 0 ] > 64 ||    ( chromaAvailable && ( tu_cb_coded_flag[ xC ][yC ] | |    tu_cr_coded_flag[ xC ][ yC ] ) ) ) &&    treeType !=DUAL_TREE_LUMA && sh_cu_chroma_qp_offset_enable d_flag &&   !IsCuChromaQpOffsetCoded ) {   cu_chroma_qp_offset_flag ae(v)   if(cu_chroma_qp_offset_flag && pps_chroma_qp_offset_list_len_minus1 > 0 )   cu_chroma_qp_offset_idx ae(v)  }  if( sps_joint_cbcr_enabled_flag &&( ( CuPredMode[ chType ][ x0 ][ y0 ] = = MODE_INTRA    && (tu_cb_coded_flag[ xC ][ yC ] | | tu_cr_coded_flag[ xC ][ yC ] ) ) | |   ( tu_cb_coded_flag[ xC ][ yC ] && tu_cr_coded_flag[ xC ][ yC ] ) ) &&   chromaAvailable )   tu_joint_cbcr_residual_flag[ xC ][ yC ] ae(v) if( tu_y_coded_flag[ x0 ][ y0 ] && treeType != DUAL_TREE_CHROMA ) {  if( sps_transform_skip_enabled_flag && !BdpcmFlag[ x0 ][ y0 ][ 0 ] &&    tbWidth <= MaxTsSize && tbHeight <= MaxTsSize &&     (IntraSubPartitionsSplitType = = ISP_NO_SPLIT ) && !cu_sbt_flag )   transform_skip_flag[ x0 ][ y0 ][ 0 ] ae(v)   if(!transform_skip_flag[ x0 ][ y0 ][ 0 ] | |sh_ts_residual_coding_disabled_fla g )    residual_coding( x0, y0, Log2(tbWidth ), Log2( tbHeight), 0 )   else    residual_ts_coding( x0, y0,Log2( tbWidth ), Log2( tbHeight), 0 )  }  if( tu_cb_coded_flag[ xC ][ yC] && treeType != DUAL_TREE_LUMA ) {   if(sps_transform_skip_enabled_flag && !BdpcmFlag[ x0 ][ y0 ][ 1 ] &&     wC<= MaxTsSize && hC <= MaxTsSize && !cu sbt flag )   transform_skip_flag[ xC ][ yC ][ 1 ] ae(v)   if(!transform_skip_flag[ xC ][ yC ][ 1 ] | |sh_ts_residual_coding_disabled_fl ag )    residual_coding( xC, yC, Log2(wC ), Log2( hC ), 1 )   else    residual_ts_coding( xC, yC, Log2( wC ),Log2( hC ), 1 )  }  if( tu_cr_coded_flag[ xC ][ yC ] && treeType !=DUAL_TREE_LUMA &&    !( tu_cb_coded_flag[ xC ][ yC ] &&tu_joint_cbcr_residual_flag[ xC ][ y C ] ) ) {   if(sps_transform_skip_enabled_flag && !BdpcmFlag[ x0 ][ y0 ][ 2 ] &&     wC<= MaxTsSize && hC <= MaxTsSize && !cu_sbt_flag )    transform_skip_flag[ xC ][ yC ][ 2 ] ae(v)   if( !transform_skip_flag[ xC ][ yC ][ 2 ]| | sh_ts_residual_coding_disabled_fl ag )    residual_coding( xC, yC,Log2( wC ), Log2( hC ), 2 )   else    residual_ts_coding( xC, yC, Log2(wC ), Log2( hC ), 2 )  } }

transform_skip_flag indicates whether transform is skipped in anassociated block. The transform_skip_flag may be a syntax element of atransform skip flag. The associated block may be a coding block (CB) ora transform block (TB). Regarding transform (and quantization) andresidual coding procedures, CB and TB may be used interchangeably. Forexample, as described above, residual samples may be derived for CB, and(quantized) transform coefficients may be derived through transform andquantization for the residual samples, and through the residual codingprocedure, information (e.g., syntax elements) efficiently indicating aposition, magnitude, sign, etc. of the (quantized) transformcoefficients may be generated and signaled. The quantized transformcoefficients may simply be called transform coefficients. In general,when the CB is not larger than a maximum TB, a size of the CB may be thesame as a size of the TB, and in this case, a target block to betransformed (and quantized) and residual coded may be called a CB or aTB. Meanwhile, when the CB is greater than the maximum TB, a targetblock to be transformed (and quantized) and residual coded may be calleda TB. Hereinafter, it will be described that syntax elements related toresidual coding are signaled in units of transform blocks (TBs) but thisis an example and the TB may be used interchangeably with coding blocks(CBs as described above.

Meanwhile, syntax elements which are signaled after the transform skipflag is signaled may be the same as the syntax elements disclosed inTable 2 and/or Table 3 below, and detailed descriptions on the syntaxelements are described below.

TABLE 2 Descriptor residual_coding( x0, y0, log2TbWidth, log2TbHeight,cIdx ) {  if( sps_mts_enabled_flag && cu_sbt_flag && cIdx = = 0 &&   log2TbWidth = = 5 && log2TbHeight < 6 )   log2ZoTbWidth = 4  else  log2ZoTbWidth = Min( log2TbWidth, 5 )  if( sps_mts_enabled_flag &&cu_sbt_flag && cIdx = = 0 &&    log2TbWidth < 6 && log2TbHeight = = 5 )  log2ZoTbHeight = 4  else   log2ZoTbHeight = Min( log2TbHeight, 5 ) if( log2TbWidth > 0 )   last_sig_coeff_x_prefix ae(v)  if(log2TbHeight > 0 )   last_sig_coeff_y_prefix ae(v)  if(last_sig_coeff_x_prefix > 3 )   last_sig_coeff_x_suffix ae(v)  if(last_sig_coeff_y_prefix > 3 )   last_sig_coeff_y_suffix ae(v) log2TbWidth = log2ZoTbWidth  log2TbHeight = log2ZoTbHeight remBinsPass1 = ( ( 1 << ( log2TbWidth + log2TbHeight ) ) * 7 ) >> 2 log2SbW = ( Min( log2TbWidth, log2TbHeight ) < 2 ? 1 : 2 )  log2SbH =log2SbW  if( log2TbWidth + log2TbHeight > 3 )   if( log2TbWidth < 2 ) {   log2SbW = log2TbWidth    log2SbH = 4 − log2SbW   } else if(log2TbHeight < 2 ) {    log2SbH = log2TbHeight    log2SbW = 4 − log2SbH  }  numSbCoeff = 1 << ( log2SbW + log2SbH )  lastScanPos = numSbCoeff lastSubBlock = ( 1 << ( log2TbWidth + log2TbHeight − ( log2SbW + log2SbH ) ) ) − 1  do {   if( lastScanPos = = 0 ) {    lastScanPos =numSbCoeff    lastSubBlock− −   }   lastScanPos− −   xS = DiagScanOrder[log2TbWidth − log2SbW ][ log2TbHeight − log2SbH ]         [ lastSubBlock][ 0 ]   yS = DiagScanOrder[ log2TbWidth − log2SbW ][ log2TbHeight −log2SbH ]         [ lastSubBlock ][ 1 ]   xC = ( xS << log2SbW ) +DiagScanOrder[ log2SbW ][ log2SbH ][ lastScan Pos ][ 0 ]   yC = ( yS <<log2SbH ) + DiagScanOrder[ log2SbW ][ log2SbH ][ lastScan Pos ][ 1 ]  }while( ( xC != LastSignificantCoeffX ) | | ( yC != LastSignificantCoeffY) )  if( lastSubBlock = = 0 && log2TbWidth >= 2 && log2TbHeight >= 2 & &   !transform_skip_flag[ x0 ][ y0 ][ cIdx ] && lastScanPos > 0 )  LfnstDcOnly = 0  if( ( lastSubBlock > 0 && log2TbWidth >= 2 &&log2TbHeight >= 2 ) | |    ( lastScanPos > 7 && ( log2TbWidth = = 2 | |log2TbWidth = = 3 ) & &    log2TbWidth = = log2TbHeight ) )  LfnstZeroOutSigCoeffFlag = 0  if( ( lastSubBlock > 0 | | lastScanPos >0 ) && cIdx = = 0 )   MtsDcOnly = 0  QState = 0  for( i = lastSubBlock;i >= 0; i− − ) {   startQStateSb = QState   xS = DiagScanOrder[log2TbWidth − log2SbW ][ log2TbHeight − log2SbH ]         [ i ][ 0 ]  yS = DiagScanOrder[ log2TbWidth − log2SbW ][ log2TbHeight − log2SbH ]        [ i ][ 1 ]   inferSbDcSigCoeffFlag = 0   if( i < lastSubBlock &&i > 0 ) {    sb_coded_flag[ xS ][ yS ] ae(v)    inferSbDcSigCoeffFlag =1   }   if( sb_coded_flag[ xS ][ yS ] && ( xS > 3 | | yS > 3 ) && cIdx == 0 )    MtsZeroOutSigCoeffFlag = 0   firstSigScanPosSb = numSbCoeff  lastSigScanPosSb = −1   firstPosMode0 = ( i = = lastSubBlock ?lastScanPos : numSbCoeff − 1 )   firstPosMode1 = firstPosMode0   for( n= firstPosMode0; n >= 0 && remBinsPass1 >= 4; n− − ) {    xC = ( xS <<log2SbW ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 0 ]    yC = ( yS<< log2SbH ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]    if(sb_coded_flag[ xS ][ yS ] && ( n > 0 | | !inferSbDcSigCoeffFlag ) & &     ( xC != LastSignificantCoeffX | | yC != Last SignificantCoeffY ) ){     sig_coeff_flag[ xC ][ yC ] ae(v)     remBinsPass1− −     if(sig_coeff_flag[ xC ][ yC ] )      inferSbDcSigCoeffFlag = 0    }    if(sig_coeff_flag[ xC ][ yC ] ) {     abs_level_gtx_flag[ n ][ 0 ] ae(v)    remBinsPass1− −     if( abs_level_gtx_flag[ n ][ 0 ] ) {     par_level_flag[ n ] ae(v)      remBinsPass1− −     abs_level_gtx_flag[ n ][ 1 ] ae(v)      remBinsPass1− −     }    if( lastSigScanPosSb = = −1 )      lastSigScanPosSb = n    firstSigScanPosSb = n    }    AbsLevelPass1[ xC [ yC ] =sig_coeff_flag[ xC ][ yC ] + par_level_flag [ n ] +          abs_level_gtx_flag[ n ][ 0 ] + 2 * abs_level_gtx_flag[ n ] [ 1]    if( sh_dep_quant_used_flag )     QState = QStateTransTable[ QState][ AbsLevelPass1[ xC ][ yC ] & 1 ]    firstPosMode1 = n − 1   }   for( n= firstPosMode0; n > firstPosMode1; n− − ) {    xC = ( xS << log2SbW ) +DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 0 ]    yC = ( yS << log2SbH) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]    if(abs_level_gtx_flag[ n ][ 1 ] )     abs_remainder[ n ] ae(v)    AbsLevel[xC ][ yC ] = AbsLevelPass1[ xC ][ yC ] +2 * abs_remainder[ n ]   }  for( n = firstPosMode1; n >= 0; n− − ) {    xC = ( xS << log2SbW ) +DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 0 ]    yC = ( yS << log2SbH) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]    if( sb_coded_flag[xS ][ yS ] )     dec_abs_level[ n ] ae(v)    if( AbsLevel[ xC ][ yC ] >0 ) {     if( lastSigScanPosSb = = −1 )      lastSigScanPosSb = n    firstSigScanPosSb = n    }    if( sh_dep_quant_used_flag )    QState = QStateTransTable[ QState ][ AbsLevel[ xC ][ yC ] & 1 ]   }  if( sh_dep_quant_used_flag | | !sh_sign_data_hiding_used_flag )   signHidden = 0   else    signHidden = ( lastSigScanPosSb −firstSigScanPosSb > 3 ? 1 : 0 )   for( n = numSbCoeff − 1; n >= 0; n− −) {    xC = ( xS << log2SbW ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ][ 0 ]    yC = ( yS << log2SbH ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n] [ 1 ]    if( ( AbsLevel[ xC ][ yC ] > 0 ) &&     ( !signHidden | | ( n!= firstSigScanPosSb ) ) )     coeff_sign_flag[ n ] ae(v)   }   if(sh_dep_quant_used_flag ) {    QState = startQStateSb    for( n =numSbCoeff − 1; n >= 0; n− − ) {     xC = ( xS << log2SbW ) +DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 0 ]     yC = ( yS << log2SbH) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]     if( AbsLevel[ xC][ yC ] > 0 )      TransCoeffLevel[ x0 ][ y0 ][ cIdx ][ xC ][ yC ] =       ( 2 * AbsLevel[ xC ][ yC ] − ( QState > 1 ? 1 : 0 ) ) *        (1 − 2 * coeff sign flag[ n ] )     QState = QStateTransTable[ QState ][AbsLevel[ xC ][ yC ] & 1 ]   } else {    sumAbsLevel = 0    for( n =numSbCoeff − 1; n >= 0; n− − ) {     xC = ( xS << log2SbW ) +DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 0 ]     yC = ( yS << log2SbH) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]     if( AbsLevel[ xC][ yC ] > 0 ) {      TransCoeffLevel[ x0 ][ y0 ][ cIdx ][ xC ][ yC ] =       AbsLevel[ xC ][ yC ] * ( 1 − 2 * coeff_sign_flag[ n ] )      if(signHidden ) {       sumAbsLevel += AbsLevel[ xC ][ yC ]       if( ( n == firstSigScanPosSb ) && ( sumAbsLevel % 2 ) = = 1 ) )       TransCoeffLevel[ x0 ][ y0 ][ cIdx ][ xC ][ yC ] =         −TransCoeffLevel[ x0 ][ y0 ][ cIdx ][ xC ][ yC ]      }     }   }   }  } }

TABLE 3 Descriptor residual_ts_coding( x0, y0, log2TbWidth,log2TbHeight, cIdx ) {  log2SbW = ( Min( log2TbWidth, log2TbHeight ) < 2? 1 : 2 )  log2SbH = log2SbW  if( log2TbWidth + log2TbHeight > 3 )   if(log2TbWidth < 2 ) {    log2SbW = log2TbWidth    log2SbH = 4 − log2SbW  } else if( log2TbHeight < 2 ) {    log2SbH = log2TbHeight    log2SbW =4 − log2SbH   }  numSbCoeff = 1 << ( log2SbW + log2SbH )  lastSubBlock =( 1 << ( log2TbWidth + log2TbHeight − ( log2SbW + log2Sb H ) ) ) − 1 inferSbCbf = 1  RemCcbs = ( ( 1 << ( log2TbWidth + log2TbHeight ) ) * 7) >> 2  for( i =0; i <= lastSubBlock; i++ ) {   xS = DiagScanOrder[log2TbWidth − log2SbW ][ log2TbHeight − log2SbH ] [ i ][ 0 ]   yS =DiagScanOrder[ log2TbWidth − log2SbW ][ log2TbHeight − log2SbH ] [ i ][1 ]   if( i != lastSubBlock | | !inferSbCbf )    sb_coded_flag[ xS ][ yS] ae(v)   if( sb_coded_flag[ xS ][ yS ] && i < lastSubBlock )   inferSbCbf = 0  /* First scan pass */   inferSbSigCoeffFlag = 1  lastScanPosPass1 = −1   for( n = 0; n <= numSbCoeff − 1 && RemCcbs >=4; n++ ) {    xC = ( xS << log2SbW ) + DiagScanOrder[ log2SbW ][ log2SbH][ n ] [ 0 ]    yC = ( yS << log2SbH ) + DiagScanOrder[ log2SbW ][log2SbH ][ n ] [ 1 ]    lastScanPosPass1 = n    if( sb_coded_flag[ xS ][yS ] &&      ( n != numSbCoeff − 1 | | !inferSbSigCoeffFlag ) ) {    sig_coeff_flag[ xC ][ yC ] ae(v)     RemCcbs− −     if(sig_coeff_flag[ xC ][ yC ] )      inferSbSigCoeffFlag = 0    }   CoeffSignLevel[ xC ][ yC ] = 0    if( sig_coeff_flag[ xC ][ yC ] ) {    coeff_sign_flag[ n ] ae(v)     RemCcbs− −     CoeffSignLevel[ xC ][yC ] = ( coeff_sign_flag[ n ] > 0 ? −1 : 1 )     abs_level_gtx_flag[ n][ 0 ] ae(v)     RemCcbs− −     if( abs_level_gtx_flag[ n ][ 0 ] ) {     par_level_flag[ n ] ae(v)      RemCcbs− −     }    }   AbsLevelPass1[ xC ][ yC ] =      sig_coeff_flag[ xC ][ yC ] +par_level_flag[ n ] + abs_level_gtx_flag [ n ][ 0 ]   }  /* Greater thanX scan pass (numGtXFlags=5) */   lastScanPosPass2 = −1   for( n = 0; n<= numSbCoeff − 1 && RemCcbs >= 4; n++ ) {    xC = ( xS << log2SbW ) +DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 0 ]    yC = ( yS << log2SbH) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]    AbsLevelPass2[ xC][ yC ] = AbsLevelPass1[ xC ][ yC ]    for( j = 1; j < 5; j++ ) {    if( abs_level_gtx_flag[ n ][ j − 1 ] ) {      abs_level_gtx_flag[ n][ j ] ae(v)      RemCcbs− −     }     AbsLevelPass2[ xC ][ yC ] += 2 *abs_level_gtx_flag[ n ][ j ]    }    lastScanPosPass2 = n   }  /*remainder scan pass */   for( n = 0; n <= numSbCoeff − 1; n++ ) {    xC= ( xS << log2SbW ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 0 ]   yC = ( yS << log2SbH ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1]    if( ( n <= lastScanPosPass2 && AbsLevelPass2[ xC ][ yC ] >= 10 ) ||      (n > lastScanPosPass2 && n <= lastScanPosPass1 &&     AbsLevelPass1[ xC ][ yC ] >= 2 ) | |      ( n > lastScanPosPass1 &&sb_coded_flag[ xS ][ yS ] ) )     abs_remainder[ n ] ae(v)    if( n <=lastScanPosPass2 )     AbsLevel[ xC ][ yC ] = AbsLevelPass2[ xC ][ yC] + 2 * abs_remainder [ n ]    else if(n <= lastScanPosPass1 )    AbsLevel[ xC ][ yC ] = AbsLevelPass1[ xC ][ yC ] + 2 * abs_remainder[ n ]    else { /* bypass */     AbsLevel[ xC ][ yC ] = abs_remainder[ n]     if( abs_remainder[ n ] )      coeff_sign_flag[ n ] ae(v)    }   if( BdpcmFlag[ x0 ][ y0 ][ cIdx ] = = 0 && n <= lastScanPosPass1 ) {    absLeftCoeff = xC > 0 ? AbsLevel[ xC − 1 ][ yC ] ) : 0    absAboveCoeff = yC > 0 ? AbsLevel[ xC ][ yC − 1 ] ) : 0    predCoeff = Max( absLeftCoeff, absAboveCoeff )     if( AbsLevel[ xC][ yC ] = = 1 && predCoeff > 0 )      AbsLevel[ xC ][ yC ] = predCoeff    else if( AbsLevel[ xC ][ yC ] > 0 && AbsLevel[ xC ][ yC ] <= predCoeff )      AbsLevel[ xC ][ yC ]− −    }    TransCoeffLevel[ x0 ][ y0 ][cIdx ][ xC ][ yC ] = ( 1 − 2 * coeff_sign_flag [ n ] ) *      AbsLevel[xC ][ yC ]   }  } }

According to the present embodiment, as shown in Table 1, residualcoding may be divided according to a value of the syntax elementtransform_skip_flag of the transform skip flag. That is, a differentsyntax element may be used for residual coding based on the value of thetransform skip flag (based on whether the transform is skipped).Residual coding used when the transform skip is not applied (that is,when the transform is applied) may be called regular residual coding(RRC), and residual coding used when the transform skip is applied (thatis, when the transform is not applied) may be called transform skipresidual coding (TSRC). Also, the regular residual coding may bereferred to as general residual coding. Also, the regular residualcoding may be referred to as a regular residual coding syntax structure,and the transform skip residual coding may be referred to as a transformskip residual coding syntax structure. Table 2 above may show a syntaxelement of residual coding when a value of transform_skip_flag is 0,that is, when the transform is applied, and Table 3 above may show asyntax element of residual coding when the value of transform_skip_flagis 1, that is, when the transform is not applied.

Specifically, for example, the transform skip flag indicating whether toskip the transform of the transform block may be parsed, and whether thetransform skip flag is 1 may be determined. If the value of thetransform skip flag is 0, as shown in Table 2, syntax elementslast_sig_coeff_x_prefix, last_sig_coeff_y_prefix,last_sig_coeff_x_suffix, last_sig_coeff_y_suffix, sb_coded_flag,sig_coeff_flag, abs_level_gtx_flag, par_level_flag, abs_remainder,coeff_sign_flag and/or dec_abs_level for a residual coefficient of thetransform block may be parsed, and the residual coefficient may bederived based on the syntax elements. In this case, the syntax elementsmay be sequentially parsed, and a parsing order may be changed. Inaddition, the abs_level_gtx_flag may represent abs_level_gt1_flag,and/or abs_level_gt3_flag. For example, abs_level_gtx_flag[n][0] may bean example of a first transform coefficient level flag(abs_level_gt1_flag), and the abs_level_gtx_flag[n][1] may be an exampleof a second transform coefficient level flag (abs_level_gt3_flag).

Referring to the Table 2 above, last_sig_coeff_x_prefix,last_sig_coeff_y_prefix, last_sig_coeff_x_suffix,last_sig_coeff_y_suffix, sb_coded_flag, sig_coeff_flag,abs_level_gt1_flag, par_level_flag, abs_level_gt3_flag, abs_remainder,coeff_sign_flag, and/or dec_abs_level may be encoded/decoded. Meanwhile,sb_coded_flag may be represented as coded_sub_block_flag.

In an embodiment, the encoding apparatus may encode (x, y) positioninformation of the last non-zero transform coefficient in a transformblock based on the syntax elements last_sig_coeff_x_prefix,last_sig_coeff_y_prefix, last_sig_coeff_x_suffix, andlast_sig_coeff_y_suffix. More specifically, the last_sig_coeff_x_prefixrepresents a prefix of a column position of a last significantcoefficient in a scanning order within the transform block, thelast_sig_coeff_y_prefix represents a prefix of a row position of thelast significant coefficient in the scanning order within the transformblock, the last_sig_coeff_x_suffix represents a suffix of a columnposition of the last significant coefficient in the scanning orderwithin the transform block, and the last_sig_coeff_y_suffix represents asuffix of a row position of the last significant coefficient in thescanning order within the transform block. Here, the significantcoefficient may represent a non-zero coefficient. In addition, thescanning order may be a right diagonal scanning order. Alternatively,the scanning order may be a horizontal scanning order or a verticalscanning order. The scanning order may be determined based on whetherintra/inter prediction is applied to a target block (a CB or a CBincluding a TB) and/or a specific intra/inter prediction mode.

Thereafter, the encoding apparatus may divide the transform block into4×4 sub-blocks, and then indicate whether there is a non-zerocoefficient in the current sub-block using a 1-bit syntax elementcoded_sub_block_flag for each 4×4 sub-block.

If a value of coded_sub_block_flag is 0, there is no more information tobe transmitted, and thus, the encoding apparatus may terminate theencoding process on the current sub-block. Conversely, if the value ofcoded_sub_block_flag is 1, the encoding apparatus may continuouslyperform the encoding process on sig_coeff_flag. Since the sub-blockincluding the last non-zero coefficient does not require encoding forthe coded_sub_block_flag and the sub-block including the DC informationof the transform block has a high probability of including the non-zerocoefficient, coded_sub_block_flag may not be coded and a value thereofmay be assumed as 1.

If the value of coded_sub_block_flag is 1 and thus it is determined thata non-zero coefficient exists in the current sub-block, the encodingapparatus may encode sig_coeff_flag having a binary value according to areverse scanning order. The encoding apparatus may encode the 1-bitsyntax element sig_coeff_flag for each transform coefficient accordingto the scanning order. If the value of the transform coefficient at thecurrent scan position is not 0, the value of sig_coeff_flag may be 1.Here, in the case of a subblock including the last non-zero coefficient,sig_coeff_flag does not need to be encoded for the last non-zerocoefficient, so the coding process for the sub-block may be omitted.Level information coding may be performed only when sig_coeff_flag is 1,and four syntax elements may be used in the level information encodingprocess. More specifically, each sig_coeff_flag[xC][yC] may indicatewhether a level (value) of a corresponding transform coefficient at eachtransform coefficient position (xC, yC) in the current TB is non-zero.In an embodiment, the sig_coeff_flag may correspond to an example of asyntax element of a significant coefficient flag indicating whether aquantized transform coefficient is a non-zero significant coefficient.

A level value remaining after encoding for sig_coeff_flag may be derivedas shown in the following equation. That is, the syntax elementremAbsLevel indicating a level value to be encoded may be derived fromthe following equation.

remAbsLevel=|coeff|−1  [Equation 1]

Herein, coeff means an actual transform coefficient value.

Additionally, abs_level_gt1_flag may indicate whether or notremAbsLevel′ of the corresponding scanning position (n) is greaterthan 1. For example, when the value of abs_level_gt1_flag is 0, theabsolute value of the transform coefficient of the correspondingposition may be 1. In addition, when the value of the abs_level_gt1_flagis 1, the remAbsLevel indicating the level value to be encoded later maybe updated as shown in the following equation.

remAbsLevel=remAbsLevel−1  [Equation 2]

In addition, the least significant coefficient (LSB) value ofremAbsLevel described in Equation 2 described above may be encoded as inEquation 3 below through par_level_flag.

par_level_flag=|coeff|& 1  [Equation 3]

Herein, par_level_flag[n] may indicate a parity of a transformcoefficient level (value) at a scanning position n.

A transform coefficient level value remAbsLevel that is to be encodedafter performing par_level_flag encoding may be updated as shown belowin the following equation.

remAbsLevel=remAbsLevel>>1  [Equation 4]

abs_level_gt3_flag may indicate whether or not remAbsLevel′ of thecorresponding scanning position (n) is greater than 3. Encoding forabs_remainder may be performed only in a case where rem_abs_gt3_flag isequal to 1. A relationship between the actual transform coefficientvalue coeff and each syntax element may be as shown below in thefollowing equation.

|coeff|=sig_coeff_flag+abs_level_gt1_flag+par_level_flag+2*(abs_level_gt3_flag+abs_remainder)  [Equation5]

Additionally, the following table indicates examples related to theabove-described Equation 5.

TABLE 4 |coeff[n]| sig_coeff_flag[n] abs_level_gtX_flag[n][0]par_level_flag[n] abs_level_gtX_flag[n][1] abs_remainder[n] 0 0 1 1 0 21 1 0 0 3 1 1 1 0 4 1 1 0 1 0 5 1 1 1 1 0 6 1 1 0 1 1 7 1 1 1 1 1 8 1 10 1 2 9 1 1 1 1 2 10 1 1 0 1 3 11 1 1 1 1 3 . . . . . . . . . . . . . .. . . .

Herein, |coeff| indicates a transform coefficient level (value) and mayalso be indicates as an AbsLevel for a transform coefficient.Additionally, a sign of each coefficient may be encoded by usingcoeff_sign_flag, which is a 1-bit symbol.

Also, if the value of the transform_skip_flag is 1, as shown in Table 3,syntax elements sb_coded_flag, sig_coeff_flag, coeff_sign_flag,abs_level_gtx_flag, par_level_flag and/or abs_remainder for a residualcoefficient of the transform block may be parsed, and the residualcoefficient may be derived based on the syntax elements. In this case,the syntax elements may be sequentially parsed, and a parsing order maybe changed. In addition, the abs_level_gtx_flag may representabs_level_gt1_flag, abs_level_gt3_flag, abs_level_gt5_flag,abs_level_gt7_flag, and/or abs_level_gt9_flag. For example,abs_level_gtx_flag[n][j] may be a flag indicating whether an absolutevalue or a level (a value) of a transform coefficient at a scanningposition n is greater than (j<<1)+1. The condition (j<<1)+1 may beoptionally replaced with a specific threshold such as a first threshold,a second threshold, or the like.

Meanwhile, CABAC provides high performance, but disadvantageously haspoor throughput performance. This is caused by a regular coding engineof the CABAC. Regular encoding (i.e., coding through the regular codingengine of the CABAC) shows high data dependence since it uses aprobability state and range updated through coding of a previous bin,and it may take a lot of time to read a probability interval anddetermine a current state. The throughput problem of the CABAC may besolved by limiting the number of context-coded bins. For example, asshown in Table 2 described above, a sum of bins used to expresssig_coeff_flag, abs_level_gt1_flag, par_level_flag, andabs_level_gt3_flag may be limited to the number of bins depending on asize of a corresponding block. Also, for example, as shown in Table 3described above, a sum of bins used to express sig_coeff_flag,coeff_sign_flag, abs_level_gt1_flag, par_level_flag, abs_level_gt3_flagabs_level_gt5_flag, abs_level_gt7_flag, abs_level_gt9_flag may belimited to the number of bins depending on a size of a correspondingblock. For example, if the corresponding block is a block of a 4×4 size,the sum of bins for the sig_coeff_flag, abs_level_gt1_flag,par_level_flag, abs_level_gt3_flag or sig_coeff_flag, coeff_sign_flag,abs_level_gt1_flag, par_level_flag, abs_level_gt3_flagabs_level_gt5_flag, abs_level_gt7_flag, abs_level_gt9_flag may belimited to 32 (or ex. 28), and if the corresponding block is a block ofa 2×2 size, the sum of bins for the sig_coeff_flag, abs_level_gt1_flag,par_level_flag, abs_level_gt3_flag may be limited to 8 (or ex. 7). Thelimited number of bins may be represented by remBinsPass1 or RemCcbs.Or, for example, for higher CABAC throughput, the number of contextcoded bins may be limited for a block (CB or TB) including a codingtarget CG. In other words, the number of context coded bins may belimited in units of blocks (CB or TB). For example, when the size of thecurrent block is 16×16, the number of context coded bins for the currentblock may be limited to 1.75 times the number of pixels of the currentblock, i.e., 448, regardless of the current CG.

In this case, if all context-coded bins of which the number is limitedare used when a context element is coded, the encoding apparatus maybinarize the remaining coefficients through a method of binarizing thecoefficient as described below, instead of using the context coding, andmay perform bypass encoding. In other words, for example, if the numberof context-coded bins which are coded for 4×4 CG is 32 (or ex. 28), orif the number of context-coded bins which are coded for 2×2 CG is 8 (orex. 7), sig_coeff_flag, abs_level_gt1_flag, par_level_flag,abs_level_gt3_flag which are coded with the context-coded bin may nolonger be coded, and may be coded directly to dec_abs_level. Or, forexample, when the number of context coded bins coded for a 4×4 block is1.75 times the number of pixels of the entire block, that is, whenlimited to 28, the sig_coeff_flag, abs_level_gt1_flag, par_level_flag,and abs_level_gt3_flag coded as context coded bins may not be coded anymore, and may be directly coded as dec_abs_level as shown in Table 5below.

TABLE 5 |coeff[n]| dec_abs_level[n] 0 0 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 89 9 10 10 11 11 . . . . . .

A value |coeff| may be derived based on dec_abs_level. In this case, atransform coefficient value, i.e., |coeff|, may be derived as shown inthe following equation.

|coeff|=dec_abs_level  [Equation 6]

In addition, the coeff_sign_flag may indicate a sign of a transformcoefficient level at a corresponding scanning position n. That is, thecoeff_sign_flag may indicate the sign of the transform coefficient atthe corresponding scanning position n.

FIG. 11 shows an example of transform coefficients in a 4×4 block.

The 4×4 block of FIG. 11 represents an example of quantizedcoefficients. The block of FIG. 11 may be a 4×4 transform block, or a4×4 sub-block of an 8×8, 16×16, 32×32, or 64×64 transform block. The 4×4block of FIG. 11 may represent a luma block or a chroma block.

Meanwhile, as described above, when an input signal is not a binaryvalue but a syntax element, the encoding apparatus may transform theinput signal into a binary value by binarizing a value of the inputsignal. In addition, the decoding apparatus may decode the syntaxelement to derive a binarized value (e.g., a binarized bin) of thesyntax element, and may de-binarize the binarized value to derive avalue of the syntax element. The binarization process may be performedas a truncated rice (TR) binarization process, a k-th order Exp-Golomb(EGk) binarization process, a limited k-th order Exp-Golomb (limitedEGk), a fixed-length (FL) binarization process, or the like. Inaddition, the de-binarization process may represent a process performedbased on the TR binarization process, the EGk binarization process, orthe FL binarization process to derive the value of the syntax element.

For example, the TR binarization process may be performed as follows.

An input of the TR binarization process may be cMax and cRiceParam for asyntax element and a request for TR binarization. In addition, an outputof the TR binarization process may be TR binarization for symbolValwhich is a value corresponding to a bin string.

Specifically, for example, in the presence of a suffix bin string for asyntax element, a TR bin string for the syntax element may beconcatenation of a prefix bin string and the suffix bin string, and inthe absence of the suffix bin string, the TR bin string for the syntaxelement may be the prefix bin string. For example, the prefix bin stringmay be derived as described below.

A prefix value of the symbolVal for the syntax element may be derived asshown in the following equation.

prefixVal=symbolVal>>cRiceParam  [Equation 7]

Herein, prefixVal may denote a prefix value of the symbolVal. A prefix(i.e., a prefix bin string) of the TR bin string of the syntax elementmay be derived as described below.

For example, if the prefixVal is less than cMax>>cRiceParam, the prefixbin string may be a bit string of length prefixVal+1, indexed by binIdx.That is, if the prefixVal is less than cMax>>cRiceParam, the prefix binstring may be a bit string of which the number of bits is prefixVal+1,indicated by binIdx. A bin for binIdx less than prefixVal may be equalto 1. In addition, a bin for the same binIdx as the prefixVal may beequal to 0.

For example, a bin string derived through unary binarization for theprefixVal may be as shown in the following table.

TABLE 6 prefixVal Bin string 0 0 1 1 0 2 1 1 0 3 1 1 1 0 4 1 1 1 1 0 5 11 1 1 1 0 . . . binIdx 0 1 2 3 4 5

Meanwhile, if the prefixVal is not less than cMax>>cRiceParam, theprefix bin string may be a bit string in which a length iscMax>>cRiceParam and all bits are 1.

In addition, if cMax is greater than symbolVal and if cRiceParam isgreater than 0, a bin suffix bin string of a TR bin string may bepresent. For example, the suffix bin string may be derived as describedbelow.

A suffix value of the symbolVal for the syntax element may be derived asshown in the following equation.

suffixVal=symbolVal−((prefixVal)<<cRiceParam)  [Equation 8]

Herein, suffixVal may denote a suffix value of the symbolVal.

A suffix of a TR bin string (i.e., a suffix bin string) may be derivedbased on an FL binarization process for suffixVal of which a value cMaxis (1<<cRiceParam)−1.

Meanwhile, if a value of an input parameter, i.e., cRiceParam, is 0, theTR binarization may be precisely truncated unary binarization, and mayalways use the same value cMax as a possible maximum value of a syntaxelement to be decoded.

In addition, for example, the EGk binarization process may be performedas follows. A syntax element coded with ue(v) may be a syntax elementsubjected to Exp-Golomb coding.

For example, a 0-th order Exp-Golomb (EGO) binarization process may beperformed as follows.

A parsing process for the syntax element may begin with reading a bitincluding a first non-zero bit starting at a current position of abitstream and counting the number of leading bits equal to 0. Theprocess may be represented as shown in the following table.

TABLE 7 leadingZeroBits = −1 for( b = 0; !b; leadingZeroBits++ )  b =read_bits( 1 )

In addition, a variable ‘codeNum’ may be derived as shown in thefollowing equation.

codeNum=2^(leadingZeroBits)−1+read_bits(leadingZeroBits)  [Equation 9]

Herein, a value returned from read_bits(leadingZeroBits), that is, avalue indicated by read_bits(leadingZeroBits), may be interpreted asbinary representation of an unsigned integer for a most significant bitrecorded first.

A structure of an Exp-Golomb code in which a bit string is divided intoa “prefix” bit and a “suffix” bit may be represented as shown in thefollowing table.

TABLE 8 Bit string form Range of codeNum 1 0 0 1 x₀ 1 . . . 2 0 0 1 x₁x₀ 3 . . . 6 0 0 0 1 x₂ x₁ x₀  7 . . . 14 0 0 0 0 1 x₃ x₂ x₁ x₀ 15 . . .30 0 0 0 0 0 1 x₄ x₃ x₂ x₁ x₀ 31 . . . 62 . . . . . .

The “prefix” bit may be a bit parsed as described above to calculateleadingZeroBits, and may be represented by 0 or 1 of a bit string inTable 8. That is, the bit string disclosed by 0 or 1 in Table 8 abovemay represent a prefix bit string. The “suffix” bit may be a bit parsedin the computation of codeNum, and may be represented by xi in Table 8above. That is, a bit string disclosed as xi in Table 8 above mayrepresent a suffix bit string. Herein, i may be a value in the range ofLeadingZeroBits−1. In addition, each xi may be equal to 0 or 1.

A bit string assigned to the codeNum may be as shown in the followingtable.

TABLE 9 Bit string codeNum 1 0 0 1 0 1 0 1 1 2 0 0 1 0 0 3 0 0 1 0 1 4 00 1 1 0 5 0 0 1 1 1 6 0 0 0 1 0 0 0 7 0 0 0 1 0 0 1 8 0 0 0 1 0 1 0 9 .. . . . .

If a descriptor of the syntax element is ue(v), that is, if the syntaxelement is coded with ue(v), a value of the syntax element may be equalto codeNum.

In addition, for example, the EGk binarization process may be performedas follows.

An input of the EGk binarization process may be a request for EGkbinarization. In addition, the output of the EGk binarization processmay be EGk binarization for symbolVal, i.e., a value corresponding to abin string.

A bit string of the EGk binarization process for symbolVal may bederived as follows.

TABLE 10 absV = Abs( symbolVal ) stopLoop = 0 do  if( absV >= ( 1 << k )) {   put( 1 )   absV = absV − ( 1 << k )   k++  } else {   put( 0 )  while( k− − )    put( ( absV >> k ) & 1 )   stopLoop = 1  } while(!stopLoop )

Referring to Table 10 above, a binary value X may be added to an end ofa bin string through each call of put(X). Herein, X may be 0 or 1.

In addition, for example, the limited EGk binarization process may beperformed as follows.

An input of the limited EGk binarization process may be a request forlimited EGk binarization, a rice parameter riceParam, log2TransformRangeas a variable representing a binary logarithm of a maximum value, andmaxPreExtLen as a variable representing a maximum prefix extensionlength. In addition, an output of the limited EGk binarization processmay be limited EGk binarization for symbolVal as a value correspondingto an empty string.

A bit string of the limited EGk binarization process for the symbolValmay be derived as follows.

TABLE 11 codeValue = symbolVal >> riceParam PrefixExtensionLength = 0while( ( PrefixExtensionLength < maxPrefixExtensionLength ) &&   (codeValue > ( ( 2 << PrefixExtensionLength ) − 2 ) ) ) { PrefixExtensionLength++  put( 1 ) } if( PrefixExtensionLength = =maxPrefixExtensionLength )  escapeLength = log2TransformRange else { escapeLength = PrefixExtensionLength + riceParam  put( 0 ) } symbolVal= symbolVal − ( ( ( 1 << PrefixExtensionLength ) − 1 ) << riceParam )while( ( escapeLength− − ) > 0 )  put( ( symbolVal >> escapeLength ) & 1)

In addition, for example, the FL binarization process may be performedas follows.

An input of the FL binarization process may be a request for FLbinarization and cMax for the syntax element. In addition, an output ofthe FL binarization process may be FL binarization for symbolVal as avalue corresponding to a bin string.

FL binarization may be configured by using a bit string of which thenumber of bits has a fixed length of symbolVal. Herein, the fixed-lengthbit may be an unsigned integer bit string. That is, a bit string forsymbolVal as a symbol value may be derived through FL binarization, anda bit length (i.e., the number of bits) of the bit string may be a fixedlength.

For example, the fixed length may be derived as shown in the followingequation.

fixedLength=Ceil(Log2(cMax+1))  [Equation 10]

Indexing of bins for FL binarization may be a method using a value whichincreases orderly from a most significant bit to a least significantbit. For example, a bin index related to the most significant bit may bebinIdx=0.

Meanwhile, for example, a binarization process for a syntax elementabs_remainder in the residual information may be performed as follows.

An input of the binarization process for the abs_remainder may be arequest for binarization of a syntax element abs_remainder[n], a colourcomponent cIdx, and a luma position (x0, y0). The luma position (x0, y0)may indicate a top-left sample of a current luma transform block basedon the top-left luma sample of a picture.

An output of the binarization process for the abs_remainder may bebinarization of the abs_remainder (i.e., a binarized bin string of theabs_remainder). Available bin strings for the abs_remainder may bederived through the binarization process.

A rice parameter cRiceParam for the abs_remainder[n] may be derivedthrough a rice parameter derivation process performed by inputting thecolor component cIdx and luma position (x0, y0), the current coefficientscan position (xC, yC), log2TbWidth, which is the binary logarithm ofthe width of the transform block, and log2TbHeight, which is the binarylogarithm of the height of the transform block. A detailed descriptionof the rice parameter derivation process will be described later.

In addition, for example, cMax for abs_remainder[n] to be currentlycoded may be derived based on the rice parameter cRiceParam. The cMaxmay be derived as shown in the following equation.

cMax=6<<cRiceParam  [Equation 11]

Meanwhile, binarization for the abs_remainder, that is, a bin string forthe abs_remainder, may be concatenation of a prefix bin string and asuffix bin string in the presence of the suffix bin string. In addition,in the absence of the suffix bin string, the bin string for theabs_remainder may be the prefix bin string.

For example, the prefix bin string may be derived as described below.

A prefix value prefixVal of the abs_remainder[n] may be derived as shownin the following equation.

prefixVal=Min(cMax,abs_remainder[n])  [Equation 12]

A prefix of the bin string (i.e., a prefix bin string) of theabs_remainder[n] may be derived through a TR binarization process forthe prefixVal, in which the cMax and the cRiceParam are used as aninput.

If the prefix bin string is identical to a bit string in which all bitsare 1 and a bit length is 6, a suffix bin string of the bin string ofthe abs_remainder[n] may exist, and may be derived as described below.

The rice parameter deriving process for the dec_abs_level[n] may be asfollows.

An input of the rice parameter deriving process may be a colourcomponent index cIdx, a luma position (x0, y0), a current coefficientscan position (xC, yC), log2TbWidth as a binary logarithm of a width ofa transform block, and log2TbHeight as a binary logarithm of a height ofthe transform block. The luma position (x0, y0) may indicate a top-leftsample of a current luma transform block based on a top-left luma sampleof a picture. In addition, an output of the rice parameter derivingprocess may be the rice parameter cRiceParam.

For example, a variable locSumAbs may be derived similarly to a pseudocode disclosed in the following table, based on an array AbsLevel[x][y]for a transform block having the given component index cIdx and thetop-left luma position (x0, y0).

TABLE 12 locSumAbs = 0 if( xC < (1 << log2TbWidth) − 1 ) {  locSumAbs +=AbsLevel[ xC + 1 ][ yC ]  if( xC < (1 << log2TbWidth) − 2 )   locSumAbs+= AbsLevel[ xC + 2 ][ yC ]  if( yC < (1 << log2TbHeight) − 1 )  locSumAbs += AbsLevel[ xC + 1 ][ yC + 1 ] (1532) } if( yC < (1 <<log2TbHeight) − 1 ) {  locSumAbs += AbsLevel[ xC ][ yC + 1 ]  if( yC <(1 << log2TbHeight) − 2 )   locSumAbs += AbsLevel[ xC ][ yC + 2 ] }locSumAbs = Clip3( 0, 31, locSumAbs − baseLevel * 5 )

Then, based on the given variable locSumAbs, the rice parametercRiceParam may be derived as shown in the following table.

TABLE 13 locSumAbs 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 cRiceParam 0 00 0 0 0 0 1 1 1 1 1 1 1 2 2 locSumAbs 16 17 18 19 20 21 22 23 24 25 2627 28 29 30 31 cRiceParam 2 2 2 2 2 2 2 2 2 2 2 2 3 3 3 3

Also, for example, in the rice parameter derivation process forabs_remainder[n], the baseLevel may be set to 4.

Alternatively, for example, the rice parameter cRiceParam may bedetermined based on whether a transform skip is applied to a currentblock. That is, if a transform is not applied to a current TB includinga current CG, in other words, if the transform skip is applied to thecurrent TB including the current CG, the rice parameter cRiceParam maybe derived to be 1.

Also, a suffix value suffixVal of the abs_remainder may be derived asshown in the following equation.

suffixVal=abs_remainder[n]−cMax  [Equation 13]

A suffix bin string of the bin string of the abs_remainder may bederived through a limited EGk binarization process for the suffixVal inwhich k is set to cRiceParam+1, riceParam is set to cRiceParam, andlog2TransformRange is set to 15, and maxPreExtLen is set to 11.

Meanwhile, for example, a binarization process for a syntax elementdec_abs_level in the residual information may be performed as follows.

An input of the binarization process for the dec_abs_level may be arequest for binarization of a syntax element dec_abs_level[n], a colourcomponent cIdx, a luma position (x0, y0), a current coefficient scanposition (xC, yC), log2TbWidth as a binary logarithm of a width of atransform block, and log2TbHeight as a binary logarithm of a height ofthe transform block. The luma position (x0, y0) may indicate a top-leftsample of a current luma transform block based on a top-left luma sampleof a picture.

An output of the binarization process for the dec_abs_level may bebinarization of the dec_abs_level (i.e., a binarized bin string of thedec_abs_level). Available bin strings for the dec_abs_level may bederived through the binarization process.

A rice parameter cRiceParam for dec_abs_level[n] may be derived througha rice parameter deriving process performed with an input of the colourcomponent cIdx, the luma position (x0, y0), the current coefficient scanposition (xC, yC), the log2TbWidth as the binary logarithm of the widthof the transform block, and the log2TbHeight as the binary logarithm ofthe height of the transform block. The rice parameter deriving processwill be described below in detail.

In addition, for example, cMax for the dec_abs_level[n] may be derivedbased on the rice parameter cRiceParam. The cMax may be derived as shownin the following table.

cMax=6<<cRiceParam  [Equation 14]

Meanwhile, binarization for the dec_abs_level[n], that is, a bin stringfor the dec_abs_level[n], may be concatenation of a prefix bin stringand a suffix bin string in the presence of the suffix bin string. Inaddition, in the absence of the suffix bin string, the bin string forthe dec_abs_level[n] may be the prefix bin string.

For example, the prefix bin string may be derived as described below.

A prefix value prefixVal of the dec_abs_level[n] may be derived as shownin the following equation.

prefixVal=Min(cMax,dec_abs_level[n])  [Equation 15]

A prefix of the bin string (i.e., a prefix bin string) of thedec_abs_level[n] may be derived through a TR binarization process forthe prefixVal, in which the cMax and the cRiceParam are used as aninput.

If the prefix bin string is identical to a bit string in which all bitsare 1 and a bit length is 6, a suffix bin string of the bin string ofthe dec_abs_level[n] may exist, and may be derived as described below.

The rice parameter deriving process for the dec_abs_level[n] may be asfollows.

An input of the rice parameter deriving process may be a colourcomponent index cIdx, a luma position (x0, y0), a current coefficientscan position (xC, yC), log2TbWidth as a binary logarithm of a width ofa transform block, and log2TbHeight as a binary logarithm of a height ofthe transform block. The luma position (x0, y0) may indicate a top-leftsample of a current luma transform block based on a top-left luma sampleof a picture. In addition, an output of the rice parameter derivingprocess may be the rice parameter cRiceParam.

For example, a variable locSumAbs may be derived similarly to a pseudocode disclosed in the following table, based on an array AbsLevel[x][y]for a transform block having the given component index cIdx and thetop-left luma position (x0, y0).

TABLE 14 locSumAbs = 0 if( xC < (1 << log2TbWidth) − 1 ) {  locSumAbs +=AbsLevel[ xC + 1 ][ yC ]  if( xC < (1 << log2TbWidth) − 2 )   locSumAbs+= AbsLevel[ xC + 2 ][ yC ]  if( yC < (1 << log2TbHeight) − 1 )  locSumAbs += AbsLevel[ xC + 1 ][ yC + 1 ] (1532) } if( yC < (1 <<log2TbHeight) − 1 ) {  locSumAbs += AbsLevel[ xC ][ yC + 1 ]  if( yC <(1 << log2TbHeight) − 2 )   locSumAbs += AbsLevel[ xC ][ yC + 2 ] }locSumAbs = Clip3( 0, 31, locSumAbs − baseLevel * 5 )

Then, based on the given variable locSumAbs, the rice parametercRiceParam may be derived as shown in the following table.

TABLE 15 locSumAbs 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 cRiceParam 0 00 0 0 0 0 1 1 1 1 1 1 1 2 2 locSumAbs 16 17 18 19 20 21 22 23 24 25 2627 28 29 30 31 cRiceParam 2 2 2 2 2 2 2 2 2 2 2 2 3 3 3 3

Also, for example, in the rice parameter derivation process fordec_abs_level[n], the baseLevel may be set to 0, and the ZeroPos[n] maybe derived as follows.

ZeroPos[n]=(QState<2?1:2)<<cRiceParam  [Equation 16]

In addition, a suffix value suffixVal of the dec_abs_level[n] may bederived as shown in the following equation.

suffixVal=dec_abs_level[n]−cMax  [Equation 17]

A suffix bin string of the bin string of the dec_abs_level[n] may bederived through a limited EGk binarization process for the suffixVal inwhich k is set to cRiceParam+1, truncSuffixLen is set to 15, andmaxPreExtLen is set to 11.

Meanwhile, the RRC and the TSRC may have the following differences.

-   -   For example, the rice parameter cRiceParam of the syntax element        abs_remainder[ ] and dec_abs_level[ ] in the RRC may be derived        based on the locSumAbs, the look-up table and/or the baseLevel        as described above, but the rice parameter cRiceParam of the        syntax element abs_remainder[ ] in the TSRC may be derived as 1.        That is, for example, when transform skip is applied to the        current block (e.g., the current TB), the Rice parameter        cRiceParam for abs_remainder[ ] of the TSRC for the current        block may be derived as 1.    -   Also, for example, referring to Table 3 and Table 4, in the RRC,        abs_level_gtx_flag[n][0] and/or abs_level_gtx_flag[n][1] may be        signaled, but in the TSRC, abs_level_gtx_flag[n][0],        abs_level_gtx_flag[n][1], abs_level_gtx_flag[n][2],        abs_level_gtx_flag[n][3], and abs_level_gtx_flag[n][4] may be        signaled. Here, the abs_level_gtx_flag[n][0] may be expressed as        abs_level_gt1_flag or a first coefficient level flag, the        abs_level_gtx_flag[n][1] may be expressed as abs_level_gt3_flag        or a second coefficient level flag, the abs_level_gtx_flag[n][2]        may be expressed as abs_level_gt5_flag or a third coefficient        level flag, the abs_level_gtx_flag[n][3] may be expressed as        abs_level_gt7_flag or a fourth coefficient level flag, and the        abs_level_gtx_flag[n][4] may be expressed as abs_level_gt9_flag        or a fifth coefficient level flag. Specifically, the first        coefficient level flag may be a flag for whether a coefficient        level is greater than a first threshold (for example, 1), the        second coefficient level flag may be a flag for whether a        coefficient level is greater than a second threshold (for        example, 3), the third coefficient level flag may be a flag for        whether a coefficient level is greater than a third threshold        (for example, 5), the fourth coefficient level flag may be a        flag for whether a coefficient level is greater than a fourth        threshold (for example, 7), the fifth coefficient level flag may        be a flag for whether a coefficient level is greater than a        fifth threshold (for example, 9). As described above, in the        TSRC, compared to the RRC, abs_level_gtx_flag[n][0],        abs_level_gtx_flag[n][1], and abs_level_gtx_flag[n][2],        abs_level_gtx_flag[n][3], abs_level_gtx_flag[n][4] may be        further included.    -   Also, for example, in the RRC, the syntax element        coeff_sign_flag may be bypass coded, but in the TSRC, the syntax        element coeff_sign_flag may be bypass coded or context coded.

Further, for a residual sample quantization process, dependentquantization may be proposed. The dependent quantization may represent amethod dependent on a value of a transform coefficient (value of atransform coefficient level) in which a reconstructed value set allowedfor a current transform coefficient precedes the current transformcoefficient in a reconstruction order. That is, for example, thedependent quantization may be realized by (a) defining two scalarquantizers having different reconstruction levels, and (b) defining aprocess for transition between the scalar quantizers. The dependentquantization may have an effect on that an allowed reconstructed vectoris more concentrated in an N-dimensional vector space in comparison tothe existing independent scalar quantization. Here, N may represent thenumber of transform coefficients of a transform block.

FIG. 12 exemplarily illustrates scalar quantizers being used independent quantization. Referring to FIG. 12 , the position of theenabled reconstructed levels may be designated by a quantization stepsize Δ. Referring to FIG. 12 , the scalar quantizers may be representedas Q0 and Q1. The scalar quantizer being used may be derived withoutbeing explicitly signaled from a bitstream. For example, the quantizerbeing used for the current transform coefficient may be determined byparities of the transform coefficient level preceding the currenttransform coefficient in the coding/reconstruction order.

FIG. 13 exemplarily illustrates the state transition and quantizerselection for the dependent quantization.

Referring to FIG. 13 , the transition between the two scalar quantizersQ0 and Q1 may be realized through a state machine having four states.The four states may have four different values (0, 1, 2, and 3). In thecoding/reconstructed order, the state for the current transformcoefficient may be determined by the parities of the transformcoefficient level prior to the current transform coefficient.

For example, in case that a dequantization process for the transformblock starts, the state for the dependent quantization may be configuredas 0. Thereafter, the transform coefficients of the transform block maybe reconstructed in the scan order (i.e., the same order as that ofentropy decoding). For example, after the current transform coefficientis reconstructed, as illustrated in FIG. 13 , the state for thedependent quantization may be updated. In the scan order, thedequantization process for the transform coefficient being reconstructedafter the current transform coefficient is reconstructed may beperformed based on an updated state. In FIG. 13 , k may represent avalue of the transform coefficient, that is, the value of the transformcoefficient level value. For example, if k (value of the currenttransform coefficient) & 1 is 0 in a state where the current state is 0,the state may be updated to 0, whereas if the k&1 is 1, the state may beupdated to 2. Further, for example, if the k&1 is 0 in a state where thecurrent state is 1, the state may be updated to 2, whereas if the k&1 is1, the state may be updated to 0. Further, for example, if the k&1 is 0in a state where the current state is 2, the state may be updated to 1,whereas if the k&1 is 1, the state may be updated to 3. Further, forexample, if the k&1 is 0 in a state where the current state is 3, thestate may be updated to 3, whereas if the k&1 is 1, the state may beupdated to 1. Referring to FIG. 13 , if the state is either 0 or 1, thescalar quantizer being used in the dequantization process may be Q0, andif the state is either 2 or 3, the scalar quantizer being used in thedequantization process may be Q1. The transform coefficient may bedequantized by the scalar quantizer for the current state based on aquantization parameter for a reconstructed level of the transformcoefficient.

Meanwhile, the present disclosure proposes embodiments related toresidual data coding. The embodiments being explained in the presentdisclosure may be combined with each other. In the residual data codingmethod as described above, regular residual coding (RRC) and transformskip residual coding (TSRC) may be present.

Of the two methods as described above, the residual data coding methodfor the current block may be determined based on values oftransform_skip_flag and sh_ts_residual_coding_disabled_flag asillustrated in Table 1. Here, the syntax elementsh_ts_residual_coding_disabled_flag may represent whether the TSRC isenabled. Accordingly, if the slice_ts_residual_coding_disabled_flagrepresents that the TSRC is not enabled even in case that thetransform_skip_flag represents the transform skip, the syntax elementsaccording to the RRC may be signaled for the transform skip block. Thatis, if the value of the transform_skip_flag is 0, or if the value of theslice_ts_residual_coding_disabled_flag is 1, the RRC may be used,whereas otherwise, the TSRC may be used.

Although high coding efficiency may be obtained in specific applications(e.g., lossless coding and the like) by using theslice_ts_residual_coding_disabled_flag, in the existing video/imagecoding standard, restrictions on a case that the dependent quantizationand the slice_ts_residual_coding_disabled_flag are used together havenot been proposed. That is, the dependent quantization may be activatedat a high level (e.g., sequence parameter set (SPS) syntax/videoparameter set (VPS) syntax/decoding parameter set (DPS) syntax/pictureheader syntax/slice header syntax) or at a low level (CU/TU), and if theslice_ts_residual_coding_disabled_flag is 1, the values dependent on thestate of the dependent quantization in the RRC may perform anunnecessary operation (i.e., operation according to the dependentquantization) to degrade the coding performance, or an unintended lossof coding performance may occur due to wrong configuration in theencoding apparatus. Accordingly, the present embodiment proposes schemesfor configuring dependencies/restrictions between two technologies ofthe dependent quantization and the residual coding (i.e., coding ofresidual samples of a transform skip block in the current slice throughthe RRC) in case that the slice_ts_residual_coding_disabled_flag=1,which are used together to prevent unintended coding loss or malfunctionfrom occurring.

As an embodiment, the present disclosure proposes a method in which theslice_ts_residual_coding_disabled_flag is dependent on theph_dep_quant_enabled_flag. For example, the syntax elements proposed inthe present embodiment may be in the following table.

TABLE 16 Descriptor slice_header( ) { picture_header_in_slice_header_flag u(1)  if(picture_header_in_slice_header_flap )    picture_header_structure!) (...)  if(!ph_dep_quant_enabled_flag)  slice_ts_residual_coding_disabled_flag u(1)   if( ph_lmcs_enabled_flag)     slice_lmcs_enabled_flag u(1)   if( pic_scaling_list_enabled_flag )    slice_scaling_list_present_flag u(1)   if( NumEntryPoints > 0 ) {    offset_len_minus1 ue(v)     for( i = 0; i < NumEntryPoints; i++ )     entry_point_offset_minus1[ i ] u(v)   }   if(slice_header_extension_present_flag ) {    slice_header_extension_length ue(v)     for( 1 = 0; i <slice_header_extension_length;     i++ )     slice_header_extension_data_byte[ i ] u(8)   }   byte_alignment( )}

According to the present embodiment, theslice_ts_residual_coding_disabled_flag may be signaled in case that thevalue of the ph_dep_quant_enabled_flag is 0. Here, theph_dep_quant_enabled_flag may represent whether the dependentquantization is enabled. For example, if the value of theph_dep_quant_enabled_flag is 1, it may represent that the dependentquantization is enabled, whereas if the value of theph_dep_quant_enabled_flag is 0, it may represent that the dependentquantization is not enabled.

Accordingly, according to the present embodiment, theslice_ts_residual_coding_disabled_flag may be signaled only in case thatthe dependent quantization is not enabled, and in case that thedependent quantization is enabled, and thus theslice_ts_residual_coding_disabled_flag is not signaled, theslice_ts_residual_coding_disabled_flag may be inferred to as 0.Meanwhile, the ph_dep_quant_enabled_flag and theslice_ts_residual_coding_disabled_flag may be signaled to the pictureheader syntax and/or the slice header syntax, or may be signaled toanother high level syntax (HLS) (e.g., SPS syntax/VPS syntax/DPS syntax)that is not the picture header syntax and the slice header syntax or atthe low level (CU/TU). If the ph_dep_quant_enabled_flag is signaled to asyntax excluding the picture header syntax, it may be called anothername. For example, the ph_dep_quant_enabled_flag may be represented asthe sh_dep_quant_enabled_flag, the sh_dep_quant_used_flag, or thesps_dep_quant_enabled_flag.

Further, the present disclosure proposes another embodiment forconfiguring dependencies/restrictions between the dependent quantizationand the residual coding (i.e., coding of residual samples of thetransform skip block in the current slice through the RRC) in case thatthe slice_ts_residual_coding_disabled_flag=1. For example, the presentembodiment proposes a scheme for making the state of the dependentquantization not in use in coding the level value of the transformcoefficient in case that the value of theslice_ts_residual_coding_disabled_flag is 1 in order to prevent theunintended coding loss or the malfunction from occurring through the useof the dependent quantization and the residual coding (i.e., coding ofresidual samples of the transform skip block in the current slicethrough the RRC) in case that theslice_ts_residual_coding_disabled_flag=1 together. The residual codingsyntax according to the present embodiment may be as in the followingtable.

TABLE 17 Descriptor residual_coding( x0, y0, log2TbWidth, log2TbHeight,cIdx ) {  if( sps_mts_enabled_flag && cu_sbt_flag && cIdx = = 0 &&   log2TbWidth = = 5 && log2TbHeight < 6 )   log2ZoTbWidth = 4  else  log2ZoTbWidth = Min( log2TbWidth, 5 )  if( sps_mts_enabled_flag &&cu_sbt_flag && cIdx = = 0 &&    log2TbWidth < 6 && log2TbHeight = = 5 )  log2ZoTbHeight = 4  else   log2ZoTbHeight = Min( log2TbHeight, 5 ) if( log2TbWidth > 0 )   last_sig_coeff_x_prefix ae(v)  if(log2TbHeight > 0 )   last_sig_coeff_y_prefix ae(v)  if(last_sig_coeff_x_prefix > 3 )   last_sig_coeff_x_suffix ae(v)  if(last_sig_coeff_y_prefix > 3 )   last_sig_coeff_y_suffix ae(v) log2TbWidth = log2ZoTbWidth  log2TbHeight = log2ZoTbHeight remBinsPass1 = ( ( 1 << ( log2TbWidth + log2TbHeight ) ) * 7 ) >> 2 log2SbW = ( Min( log2TbWidth, log2TbHeight ) < 2 ? 1 : 2 )  log2SbH =log2SbW  if( log2TbWidth + log2TbHeight > 3 )   if( log2TbWidth < 2 ) {   log2SbW = log2TbWidth    log2SbH = 4 − log2SbW   } else if(log2TbHeight < 2 ) {    log2SbH = log2TbHeight    log2SbW = 4 − log2SbH  }  numSbCoeff = 1 << ( log2SbW + log2SbH )  lastScanPos = numSbCoeff lastSubBlock = ( 1 << ( log2TbWidth + log2TbHeight − ( log2SbW + log2SbH ) ) ) − 1  do {   if( lastScanPos = = 0 ) {    lastScanPos =numSbCoeff    lastSubBlock− −   }   lastScanPos− −   xS = DiagScanOrder[log2TbWidth − log2SbW ][ log2TbHeight − log2Sb H ]         [lastSubBlock ][ 0 ]   yS = DiagScanOrder[ log2TbWidth − log2SbW ][log2TbHeight − log2Sb H ]         [ lastSubBlock ][ 1 ]   xC = ( xS <<log2SbW ) + DiagScanOrder[ log2SbW ][ log2SbH ][ lastSca nPos ][ 0 ]  yC = ( yS << log2SbH ) + DiagScanOrder[ log2SbW ][ log2SbH ][ lastScanPos ][ 1 ]  } while( ( xC != LastSignificantCoeffX ) | | ( yC !=LastSignificantCoeffY ) )  if( lastSubBlock = = 0 && log2TbWidth >= 2 &&log2TbHeight >= 2 &&    !transform_skip_flag[ x0 ][ y0 ][ cIdx ] &&lastScanPos > 0 )   LfnstDcOnly = 0  if( ( lastSubBlock > 0 &&log2TbWidth >= 2 && log2TbHeight >= 2 ) | |    ( lastScanPos > 7 && (log2TbWidth = = 2 | | log2TbWidth = = 3 ) &&    log2TbWidth = =log2TbHeight ) )   LfnstZeroOutSigCoeffFlag = 0  if( ( lastSubBlock > 0| | lastScanPos > 0 ) && cIdx = = 0 )   MtsDcOnly = 0  QState = 0  for(i = lastSubBlock; i >= 0; i− − ) {   startQStateSb = QState   xS =DiagScanOrder[ log2TbWidth − log2SbW ][ log2TbHeight − log2Sb H ]        [ i ][ 0 ]   yS = DiagScanOrder[ log2TbWidth − log2SbW ][log2TbHeight − log2Sb H ]         [ i ][ 1 ]   inferSbBcSigCoeffFlag = 0  if( i < lastSubBlock && i > 0 ) {    coded_sub_block_flag[ xS ][ yS ]ae(v)    inferSbDcSigCoeffFlag = 1   }   if( coded_sub_block_flag[ xS ][yS ] && ( xS > 3 | | yS > 3 ) & cIdx = = 0 )    MtsZeroOutSigCoeffFlag =0   firstSigScanPosSb = numSbCoeff   lastSigScanPosSb = −1  firstPosMode0 = ( i = = lastSubBlock ? lastScanPos : numSbCoeff − 1 )  firstPosMode1 = firstPosMode0   for( n = firstPosMode0; n >= 0 &&remBinsPass1 >= 4; n− − ) {    xC = ( xS << log2SbW ) + DiagScanOrder[log2SbW ][ log2SbH ][ n ] [ 0 ]    yC = ( yS << log2SbH ) +DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]    if(coded_sub_block_flag[ xS ][ yS ] && ( n > 0 | | !inferSbDcSigCoeff Flag) &&      ( xC != LastSignificantCoeffX | | yC != Last SignificantCoeffY) ) {     sig_coeff_flag[ xC ][ yC ] ae(v)     remBinsPass1− −     if(sig_coeff_flag[ xC ][ yC ] )      inferSbDcSigCoeffFlag = 0    }    if(sig_coeff_flag[ xC ][ yC ] ) {     abs_level_gtx_flag[ n ][ 0 ] ae(v)    remBinsPass1− −     if( abs_level_gtx_flag[ n ][ 0 ] ) {     par_level_flag[ n ] ae(v)      remBinsPass1− −     abs_level_gtx_flag[ n ][ 1 ] ae(v)      remBinsPass1− −     }    if( lastSigScanPosSb = = −1 )      lastSigScanPosSb = n    firstSigScanPosSb = n    }    AbsLevelPass1[ xC ][ yC ] =sig_coeff_flag[ xC ][ yC ] + par_level_flag [ n ] +     abs_level_gtx_flag[ n ][ 0 ] + 2 * abs_level_gtx_flag[ n ] [ 1 ]   if( ph_dep_quant_enabled_flag )     QState = QStateTransTable[ QState][ AbsLevelPass1[ xC ][ yC ] & 1 ]    firstPosMode1 = n − 1   }   for( n= firstPosMode0; n > firstPosMode1; n− − ) {    xC = ( xS << log2SbW ) +DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 0 ]    yC = ( yS << log2SbH) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]    if(abs_level_gtx_flag[ n ][ 1 ] )     abs_remainder[ n ] ae(v)    AbsLevel[xC ][ yC ] = AbsLevelPass1[ xC ][ yC ] +2 * abs_remainder [ n ]   }  for( n = firstPosMode1; n >= 0; n− − )    xC = ( xS << log2SbW ) +DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 0 ]    yC = ( yS << log2SbH) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]    if(coded_sub_block_flag[ xS ][ yS ] )     dec_abs_level[ n ] ae(v)    if(AbsLevel[ xC ][ yC ] > 0 ) {     if( lastSigScanPosSb = = −1 )     lastSigScanPosSb = n     firstSigScanPosSb = n    }    if(ph_dep_quant_enabled_flag )     QState = QStateTransTable[ QState ][AbsLevel[ xC ][ yC ] & 1 ]   }   if( ph_dep_quant_enabled_flag | |!pic_sign_data_hiding_endabled_flag )    signHidden = 0   else   signHidden = ( lastSigScanPosSb − firstSigScanPosSb > 3 ? 1 : 0 )  for( n = numSbCoeff − 1; n >= 0; n− − ) {    xC = ( xS << log2SbW ) +DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 0 ]    yC = ( yS << log2SbH) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]    if( ( AbsLevel[ xC][ yC ] > 0 ) &&     ( !signHidden | | ( n != firstSigScanPosSb ) ) )    coeff_sign_flag[ n ] ae(v)   }   if( ph_dep_quant_enabled_flag &&!slice_ts_residual_coding_disabled_flag ) {    QState = startQStateSb   for( n = numSbCoeff − 1; n >= 0; n− − ) {     xC = ( xS << log2SbW) + DiagScanOrder[ log2SbW ][ log2SbH ] [ n ][ 0 ]     yC = ( yS <<log2SbH ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]     if(AbsLevel[ xC ][ yC ] > 0 )      TransCoeffLevel[ x0 ][ y0 ][ cIdx ][ xC][ yC ] =        ( 2 * AbsLevel[ xC ][ yC ] − ( QState > 1 ? 1 : 0 ) ) *       ( 1 − 2 * coeff_sign_flag[ n ] )     QState = QStateTransTable[QState ][ AbsLevel[ xC ][ yC ] & 1 ]   } else {    sumAbsLevel = 0   for( n = numSbCoeff − 1 n >= 0; n− − ) {     xC = ( xS << log2SbW ) +DiagScanOrder[ log2SbW ][ log2SbH ] [ n ][ 0 ]     yC = ( yS << log2SbH) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]     if( AbsLevel[ xC][ yC ] > 0 ) {      TransCoeffLevel[ x0 ][ y0 ][ cIdx ][ xC ][ yC ] =       AbsLevel[ xC ][ yC ] * ( 1 − 2 * coeff_sign_flag[ n ] )      if(signHidden ) {       sumAbsLevel += AbsLevel[ xC ][ yC ]       if( ( n == firstSigScanPosSb ) && ( sumAbsLevel % 2 ) = = 1 ) )       TransCoeffLevel[ x0 ][ y0 ][ cIdx ][ xC ][ yC ] =         −TransCoeffLevel[ x0 ][ y0 ][ cIdx ][ xC ][ yC ]      }     }   }   }  } }

Referring to Table 17 as described above, in case that the value of theph_dep_quant_enabled_flag is 1, and the value of theslice_ts_residual_coding_disabled_flag is 0, the Qstate may be derived,and the value of the transform coefficient (transform coefficient level)may be derived based on the Qstate. For example, referring to Table 17,the transform coefficient level TransCoeffLevel[x0][y0][cIdx][xC][yC]may be derived as (2*AbsLevel[xC][yC]−(QState>1 ?1:0))*(1−2*coeff_sign_flag[n]). Here, the AbsLevel[xC][yC] may be anabsolute value of the transform coefficient derived based on the syntaxelements of the transform coefficient, the coeff_sign_flag[n] may be asyntax element of a sign flag representing the sign of the transformcoefficient, and the (QState>1 ? 1:0) may represent 1 if the value ofthe state QState is larger than 1, that is, if the value of the stateQstate is 2 or 3, and may represent 0 if the value of the state Qstateis equal to or smaller than 1, that is, if the value of the state Qstateis 0 or 1.

Further, referring to Table 17 as described above, if the value of theslice_ts_residual_coding_disabled_flag is 1, the value of the transformcoefficient (transform coefficient level) may be derived without usingthe Qstate. For example, referring to Table 17, the transformcoefficient level TransCoeffLevel[x0][y0][cIdx][xC][yC] may be derivedas AbsLevel[xC][yC]*(1−2*coeff_sign_flag[n]). Here, the AbsLevel[xC][yC]may be an absolute value of the transform coefficient derived based onthe syntax elements of the transform coefficient, and thecoeff_sign_flag[n] may be an syntax element of a sign flag representingthe sign of the transform coefficient.

Further, according to the present embodiment, if the value of theslice_ts_residual_coding_disabled_flag is 1, the state of the dependentquantization may not be used in coding the level value of the transformcoefficient, and the state update may also not be performed. Forexample, the residual coding syntax according to the present embodimentmay be as in the following table.

TABLE 18 Descriptor residual_coding( x0, y0, log2TbWidth, log2TbHeight,cIdx ) {  if( sps_mts_enabled_flag && cu_sbt_flag && cIdx = = 0 &&   log2TbWidth = = 5 && log2TbHeight < 6 )   log2ZoTbWidth = 4  else  log2ZoTbWidth = Min( log2TbWidth, 5 )  if( sps_mts_enabled_flag &&cu_sbt_flag && cIdx = = 0 &&    log2TbWidth < 6 && log2TbHeight = = 5 )  log2ZoTbHeight = 4  else   log2ZoTbHeight = Min( log2TbHeight, 5 ) if( log2TbWidth > 0 )   last_sig_coeff_x_prefix ae(v)  if(log2TbHeight > 0 )   last_sig_coeff_y_prefix ae(v)  if(last_sig_coeff_x_prefix > 3 )   last_sig_coeff_x_suffix ae(v)  if(last_sig_coeff_y_prefix > 3 )   last_sig_coeff_y_suffix ae(v) log2TbWidth = log2ZoTbWidth  log2TbHeight = log2ZoTbHeight remBinsPass1 = ( ( 1 << ( log2TbWidth + log2TbHeight ) ) * 7 ) >> 2 log2SbW = ( Min( log2TbWidth, log2TbHeight ) < 2 ? 1 : 2 )  log2SbH =log2SbW  if( log2TbWidth + log2TbHeight > 3 )   if( log2TbWidth < 2 ) {   log2SbW = log2TbWidth    log2SbH = 4 − log2SbW   } else if(log2TbHeight < 2 ) {    log2SbH = log2TbHeight    log2SbW = 4 − log2SbH  }  numSbCoeff = 1 << ( log2SbW + log2SbH )  lastScanPos = numSbCoeff lastSubBlock = ( 1 << ( log2TbWidth + log2TbHeight − ( log2SbW + log2SbH ) ) ) − 1  do {   if( lastScanPos = = 0 ) {    lastScanPos =numSbCoeff    lastSubBlock− −   }   lastScanPos− −   xS = DiagScanOrder[log2TbWidth − log2SbW ][ log2TbHeight − log2Sb H ]         [lastSubBlock ][ 0 ]   yS = DiagScanOrder[ log2TbWidth − log2SbW ][log2TbHeight − log2Sb H ]         [ lastSubBlock ][ 1 ]   xC = ( xS <<log2SbW ) + DiagScanOrder[ log2SbW ][ log2SbH ][ lastSca nPos ][ 0 ]  yC = ( yS << log2SbH ) + DiagScanOrder[ log2SbW ][ log2SbH ][ lastScanPos ][ 1 ]  } while( ( xC != LastSignificantCoeffX ) | | ( yC !=LastSignificantCoeffY ) )  if( lastSubBlock = = 0 && log2TbWidth >= 2 &&log2TbHeight >= 2 &&    !transform_skip_flag[ x0 ][ y0 ][ cIdx ] &&lastScanPos > 0 )   LfnstDcOnly = 0  if( ( lastSubBlock > 0 &&log2TbWidth >= 2 && log2TbHeight >= 2 ) | |    ( lastScanPos > 7 && (log2TbWidth = = 2 | | log2TbWidthWidth = = 3 ) &&    log2TbWidth = =log2TbHeight ) )   LfnstZeroOutSigCoeffFlag = 0  if( ( lastSubBlock > 0| | lastScanPos > 0 ) && cIdx = = 0 )   MtsDcOnly = 0  QState = 0  for(i = lastSubBlock; i >= 0; i− − ) {   startQStateSb = QState   xS =DiagScanOrder[ log2TbWidth − log2SbW ][ log2TbHeight − log2Sb H ]        [ i ][ 0 ]   yS = DiagScanOrder[ log2TbWidth − log2SbW ][log2TbHeight − log2Sb H ]         [ i ][ 1 ]   inferSbBcSigCoeffFlag = 0  if( i < lastSubBlock && i > 0 ) {    coded_sub_block_flag[ xS ][ yS ]ae(v)    inferSbDcSigCoeffFlag = 1   }   if( coded_sub_block_flag[ xS ][yS ] && ( xS > 3 | | yS > 3 ) & cIdx = = 0 )    MtsZeroOutSigCoeffFlag =0   firstSigScanPosSb = numSbCoeff   lastSigScanPosSb = −1  firstPosMode0 = ( i = = lastSubBlock ? lastScanPos : numSbCoeff − 1 )  firstPosMode1 = firstPosMode0   for( n = firstPosMode0; n >= 0 &&remBinsPass1 >= 4; n− − ) {    xC = ( xS << log2SbW ) + DiagScanOrder[log2SbW ][ log2SbH ][ n ] [ 0 ]    yC = ( yS << log2SbH ) +DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]    if(coded_sub_block_flag[ xS ][ yS ] && ( n > 0 | | !inferSbDcSigCoeff Flag) &&      ( xC != LastSignificantCoeffX | | yC != Last SignificantCoeffY) ) {     sig_coeff_flag[ xC ][ yC ] ae(v)     remBinsPass1− −     if(sig_coeff_flag[ xC ][ yC ] )      inferSbDcSigCoeffFlag = 0    }    if(sig_coeff_flag[ xC ][ yC ] ) {     abs_level_gtx_flag[ n ][ 0 ] ae(v)    remBinsPass1− −     if( abs_level_gtx_flag[ n ][ 0 ] ) {     par_level_flag[ n ] ae(v)      remBinsPass1− −     abs_level_gtx_flag[ n ][ 1 ] ae(v)      remBinsPass1− −     }    if( lastSigScanPosSb = = −1 )      lastSigScanPosSb = n    firstSigScanPosSb = n    }    AbsLevelPass1[ xC ][ yC ] =sig_coeff_flag[ xC ][ yC ] + par_level_flag [ n ] +     abs_level_gtx_flag[ n ][ 0 ] + 2 * abs_level_gtx_flag[ n ] [ 1 ]   if( ph_dep_quant_enabled_flag &&!slice_ts_residual_coding_disabled_fl ag )     QState =QStateTransTable[ QState ][ AbsLevelPass1[ xC ][ yC ] & 1 ]   firstPosMode1 = n − 1   }   for( n = firstPosMode0; n >firstPosMode1; n− − ) {    xC = ( xS << log2SbW ) + DiagScanOrder[log2SbW ][ log2SbH ][ n ] [ 0 ]    yC = ( yS << log2SbH ) +DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]    if(abs_level_gtx_flag[ n ][ 1 ] )     abs_remainder[ n ] ae(v)    AbsLevel[xC ][ yC ] = AbsLevelPass1[ xC ][ yC ] +2 * abs_remainder [ n ]   }  for( n = firstPosMode1; n >= 0; n− − )    xC = ( xS << log2SbW ) +DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 0 ]    yC = ( yS << log2SbH) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]    if(coded_sub_block_flag[ xS ][ yS ] )     dec_abs_level[ n ] ae(v)    if(AbsLevel[ xC ][ yC ] > 0 ) {     if( lastSigScanPosSb = = −1 )     lastSigScanPosSb = n     firstSigScanPosSb = n    }    if(ph_dep_quant_enabled_flag && !slice_ts_residual_coding_disabled_fl ag )    QState = QStateTransTable[ QState ][ AbsLevel[ xC ][ yC ] & 1 ]   }  if( ph_dep_quant_enabled_flag | | !pic_sign_data_hiding_endabled_flag)    signHidden = 0   else    signHidden = ( lastSigScanPosSb −firstSigScanPosSb > 3 ? 1 : 0 )     ( lastSigScanPosSb −firstSigScanPosSb > 3 ? 1 : 0 )   for( n = numSbCoeff − 1; n >= 0; n− −) {    xC = ( xS << log2SbW ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ][ 0 ]    yC = ( yS << log2SbH ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n] [ 1 ]    if( ( AbsLevel[ xC ][ yC ] > 0 ) &&     ( !signHidden | | ( n!= firstSigScanPosSb ) ) )     coeff_sign_flag[ n ] ae(v)   }   if(ph_dep_quant_enabled_flag && !slice_ts_residual_coding_disabled_flag ) {   QState = startQStateSb    for( n = numSbCoeff − 1; n >= 0; n− − ) {    xC = ( xS << log2SbW ) + DiagScanOrder[ log2SbW ][ log2SbH ] [ n ][0 ]     yC = ( yS << log2SbH ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n] [ 1 ]     if( AbsLevel[ xC ][ yC ] > 0 )      TransCoeffLevel[ x0 ][y0 ][ cIdx ][ xC ][ yC ] =        ( 2 * AbsLevel[ xC ][ yC ] − (QState > 1 ? 1 : 0 ) ) *        ( 1 − 2 * coeff_sign_flag[ n ] )    QState = QStateTransTable[ QState ][ AbsLevel[ xC ][ yC ] & 1 ]   }else {    sumAbsLevel = 0    for( n = numSbCoeff − 1 n >= 0; n− − ) {    xC = ( xS << log2SbW ) + DiagScanOrder[ log2SbW ][ log2SbH ] [ n ][0 ]     yC = ( yS << log2SbH ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n] [ 1 ]     if( AbsLevel[ xC ][ yC ] > 0 ) {      TransCoeffLevel[ x0 ][y0 ][ cIdx ][ xC ][ yC ] =        AbsLevel[ xC ][ yC ] * ( 1 − 2 *coeff_sign_flag[ n ] )      if( signHidden ) {       sumAbsLevel +=AbsLevel[ xC ][ yC ]       if( ( n = = firstSigScanPosSb ) && (sumAbsLevel % 2 ) = = 1 ) )        TransCoeffLevel[ x0 ][ y0 ][ cIdx ][xC ][ yC ] =          −TransCoeffLevel[ x0 ][ y0 ][ cIdx ][ xC ][ yC ]     }     }    }   }  } }

Referring to Table 18 as described above, if the value of theph_dep_quant_enabled_flag is 1, and the value of theslice_ts_residual_coding_disabled_flag is 0, the Qstate may be updated.For example, if the value of the ph_dep_quant_enabled_flag is 1, and thevalue of the slice_ts_residual_coding_disabled_flag is 0, the QState maybe updated as QStateTransTable[QState][AbsLevelPass1[xC][yC] & 1] orQStateTransTable[QState][AbsLevel[xC][yC] & 1]. Further, if the value ofthe slice_ts_residual_coding_disabled_flag is 1, a process of updatingthe Qstate may not be performed.

Further, referring to Table 18 as described above, if the value of theph_dep_quant_enabled_flag is 1, and the value of theslice_ts_residual_coding_disabled_flag is 0, the value of the transformcoefficient (transform coefficient level) may be derived based on theQState. For example, referring to Table 18, the transform coefficientlevel TransCoeffLevel[x0][y0][cIdx][xC][yC] may be derived as(2*AbsLevel[xC][yC]−(QState>1 ? 1:0))*(1−2*coeff_sign_flag[n]). Here,the AbsLevel[xC][yC] may be an absolute value of the transformcoefficient derived based on the syntax elements of the transformcoefficient, the coeff_sign_flag[n] may be the syntax element of thesign flag representing the sign of the transform coefficient, and the(QState>1 ? 1:0) may represent 1 if the value of the state QState islarger than 1, that is, if the value of the state Qstate is 2 or 3, andmay represent 0 if the value of the state Qstate is equal to or smallerthan 1, that is, if the value of the state Qstate is 0 or 1.

Further, referring to Table 18 as described above, if the value of theslice_ts_residual_coding_disabled_flag is 1, the value of the transformcoefficient (transform coefficient level) may be derived without usingthe Qstate. For example, referring to Table 18, the transformcoefficient level TransCoeffLevel[x0][y0][cIdx][xC][yC] may be derivedas AbsLevel[xC][yC]*(1−2*coeff_sign_flag[n]). Here, the AbsLevel[xC][yC]may be an absolute value of the transform coefficient derived based onthe syntax elements of the transform coefficient, and thecoeff_sign_flag[n] may be an syntax element of a sign flag representingthe sign of the transform coefficient.

Further, the present disclosure proposes another embodiment forconfiguring dependencies/restrictions between the dependent quantizationand the residual coding (i.e., coding of residual samples of thetransform skip block in the current slice through the RRC) in case thatthe slice_ts_residual_coding_disabled_flag=1. For example, the presentembodiment proposes a scheme for adding restrictions using atransform_skip_flag in a process of deriving the value of the transformcoefficient (transform coefficient level) dependently on the stateupdate or the state of the dependent quantization in the RRC. That is,the present embodiment proposes a scheme for making the process ofderiving the value of the transform coefficient (transform coefficientlevel) not in use dependently on the state update and/or the state ofthe dependent quantization in the RRC based on the transform_skip_flag.The residual coding syntax according to the present embodiment may be asin the following Table.

TABLE 19 Descriptor residual_coding( x0, y0, log2TbWidth, log2TbHeight,cIdx ) {  if( sps_mts_enabled_flag && cu_sbt_flag && cIdx = = 0 &&   log2TbWidth = = 5 && log2TbHeight < 6 )   log2ZoTbWidth = 4  else  log2ZoTbWidth = Min( log2TbWidth, 5 )  if( sps_mts_enabled_flag &&cu_sbt_flag && cIdx = = 0 &&    log2TbWidth < 6 && log2TbHeight = = 5 )  log2ZoTbHeight = 4  else   log2ZoTbHeight = Min( log2TbHeight, 5 ) if( log2TbWidth > 0 )   last_sig_coeff_x_prefix ae(v)  if(log2TbHeight > 0 )   last_sig_coeff_y_prefix ae(v)  if(last_sig_coeff_x_prefix > 3 )   last_sig_coeff_x_suffix ae(v)  if(last_sig_coeff_y_prefix > 3 )   last_sig_coeff_y_suffix ae(v) log2TbWidth = log2ZoTbWidth  log2TbHeight = log2ZoTbHeight remBinsPass1 = ( ( 1 << ( log2TbWidth + log2TbHeight ) ) * 7 ) >> 2 log2SbW = ( Min( log2TbWidth, log2TbHeight ) < 2 ? 1 : 2 )  log2SbH =log2SbW  if( log2TbWidth + log2TbHeight > 3 )   if( log2TbWidth < 2 ) {   log2SbW = log2TbWidth    log2SbH = 4 − log2SbW   } else if(log2TbHeight < 2 ) {    log2SbH = log2TbHeight    log2SbW = 4 − log2SbH  }  numSbCoeff = 1 << ( log2SbW + log2SbH )  lastScanPos = numSbCoeff lastSubBlock = ( 1 << ( log2TbWidth + log2TbHeight − ( log2SbW + log2SbH ) ) ) − 1  do {   if( lastScanPos = = 0 ) {    lastScanPos =numSbCoeff    lastSubBlock− −   }   lastScanPos− −   xS = DiagScanOrder[log2TbWidth − log2SbW ][ log2TbHeight − log2Sb H ]         [lastSubBlock ][ 0 ]   yS = DiagScanOrder[ log2TbWidth − log2SbW ][log2TbHeight − log2Sb H ]         [ lastSubBlock ][ 1 ]   xC = ( xS <<log2SbW ) + DiagScanOrder[ log2SbW ][ log2SbH ][ lastSca nPos ][ 0 ]  yC = ( yS << log2SbH ) + DiagScanOrder[ log2SbW ][ log2SbH ][ lastScanPos ][ 1 ]  } while( ( xC != LastSignificantCoeffX ) | | ( yC !=LastSignificantCoeffY ) )  if( lastSubBlock = = 0 && log2TbWidth >= 2 &&log2TbHeight >= 2 &&    !transform_skip_flag[ x0 ][ y0 ][ cIdx ] &&lastScanPos > 0 )   LfnstDcOnly = 0  if( ( lastSubBlock > 0 &&log2TbWidth >= 2 && log2TbHeight >= 2 ) | |    ( lastScanPos > 7 && (log2TbWidth = = 2 | | log2TbWidthWidth = = 3 ) &&    log2TbWidth = =log2TbHeight ) )   LfnstZeroOutSigCoeffFlag = 0  if( ( lastSubBlock > 0| | lastScanPos > 0 ) && cIdx = = 0 )   MtsDcOnly = 0  QState = 0  for(i = lastSubBlock; i >= 0; i− − ) {   startQStateSb = QState   xS =DiagScanOrder[ log2TbWidth − log2SbW ][ log2TbHeight − log2Sb H ]        [ i ][ 0 ]   yS = DiagScanOrder[ log2TbWidth − log2SbW ][log2TbHeight − log2Sb H ]         [ i ][ 1 ]   inferSbBcSigCoeffFlag = 0  if( i < lastSubBlock && i > 0 ) {    coded_sub_block_flag[ xS ][ yS ]ae(v)    inferSbDcSigCoeffFlag = 1   }   if( coded_sub_block_flag[ xS ][yS ] && ( xS > 3 | | yS > 3 ) & cIdx = = 0 )    MtsZeroOutSigCoeffFlag =0   firstSigScanPosSb = numSbCoeff   lastSigScanPosSb = −1  firstPosMode0 = ( i = = lastSubBlock ? lastScanPos : numSbCoeff − 1 )  firstPosMode1 = firstPosMode0   for( n = firstPosMode0; n >= 0 &&remBinsPass1 >= 4; n− − ) {    xC = ( xS << log2SbW ) + DiagScanOrder[log2SbW ][ log2SbH ][ n ] [ 0 ]    yC = ( yS << log2SbH ) +DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]    if(coded_sub_block_flag[ xS ][ yS ] && ( n > 0 | | !inferSbDcSigCoeff Flag) &&      ( xC != LastSignificantCoeffX | | yC != Last SignificantCoeffY) ) {     sig_coeff_flag[ xC ][ yC ] ae(v)     remBinsPass1− −     if(sig_coeff_flag[ xC ][ yC ] )      inferSbDcSigCoeffFlag = 0    }    if(sig_coeff_flag[ xC ][ yC ] ) {     abs_level_gtx_flag[ n ][ 0 ] ae(v)    remBinsPass1− −     if( abs_level_gtx_flag[ n ][ 0 ] ) {     par_level_flag[ n ] ae(v)      remBinsPass1− −     abs_level_gtx_flag[ n ][ 1 ] ae(v)      remBinsPass1− −     }    if( lastSigScanPosSb = = −1 )      lastSigScanPosSb = n    firstSigScanPosSb = n    }    AbsLevelPass1[ xC ][ yC ] =sig_coeff_flag[ xC ][ yC ] + par_level_flag [ n ] +     abs_level_gtx_flag[ n ][ 0 ] + 2 * abs_level_gtx_flag[ n ] [ 1 ]   if( ph_dep_quant_enabled_flag && !transform_skip_flag[ x0 ][ y0 ][cIdx ] )     QState = QStateTransTable[ QState ][ AbsLevelPass1[ xC ][yC ] & 1 ]    firstPosMode1 = n − 1   }   for( n = firstPosMode0; n >firstPosMode1; n− − ) {    xC = ( xS << log2SbW ) + DiagScanOrder[log2SbW ][ log2SbH ][ n ] [ 0 ]    yC = ( yS << log2SbH ) +DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]    if(abs_level_gtx_flag[ n ][ 1 ] )     abs_remainder[ n ] ae(v)    AbsLevel[xC ][ yC ] = AbsLevelPass1[ xC ][ yC ] +2 * abs_remainder [ n ]   }  for( n = firstPosMode1; n >= 0; n− − )    xC = ( xS << log2SbW ) +DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 0 ]    yC = ( yS << log2SbH) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]    if(coded_sub_block_flag[ xS ][ yS ] )     dec_abs_level[ n ] ae(v)    if(AbsLevel[ xC ][ yC ] > 0 ) {     if( lastSigScanPosSb = = −1 )     lastSigScanPosSb = n     firstSigScanPosSb = n    }    if(ph_dep_quant_enabled_flag && !transform_skip_flag[ x0 ][ y0 ][ cIdx ] )    QState = QStateTransTable[ QState ][ AbsLevel[ xC ][ yC ] & 1 ]   }  if( ph_dep_quant_enabled_flag | | !pic_sign_data_hiding_endabled_flag)    signHidden = 0   else    signHidden = ( lastSigScanPosSb −firstSigScanPosSb > 3 ? 1 : 0 )   for( n = numSbCoeff − 1; n >= 0; n− −) {    xC = ( xS << log2SbW ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ][ 0 ]    yC = ( yS << log2SbH ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n] [ 1 ]    if( ( AbsLevel[ xC ][ yC ] > 0 ) &&     ( !signHidden | | ( n!= firstSigScanPosSb ) ) )     coeff_sign_flag[ n ] ae(v)   }   if(ph_dep_quant_enabled_flag && !transform_skip_flag[ x0 ][ y0 ][ cIdx ] ){    QState = startQStateSb    for( n = numSbCoeff − 1; n >= 0; n− − ) {    xC = ( xS << log2SbW ) + DiagScanOrder[ log2SbW ][ log2SbH ] [ n ][0 ]     yC = ( yS << log2SbH ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n] [ 1 ]     if( AbsLevel[ xC ][ yC ] > 0 )      TransCoeffLevel[ x0 ][y0 ][ cIdx ][ xC ][ yC ] =        ( 2 * AbsLevel[ xC ][ yC ] − (QState > 1 ? 1 : 0 ) ) *        ( 1 − 2 * coeff_sign_flag[ n ] )    QState = QStateTransTable[ QState ][ AbsLevel[ xC ][ yC ] & 1 ]   }else {    sumAbsLevel = 0    for( n = numSbCoeff − 1 n >= 0; n− − ) {    xC = ( xS << log2SbW ) + DiagScanOrder[ log2SbW ][ log2SbH ] [ n ][0 ]     yC = ( yS << log2SbH ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n] [ 1 ]     if( AbsLevel[ xC ][ yC ] > 0 ) {      TransCoeffLevel[ x0 ][y0 ][ cIdx ][ xC ][ yC ] =        AbsLevel[ xC ][ yC ] * ( 1 − 2 *coeff_sign_flag[ n ] )      if( signHidden ) {       sumAbsLevel +=AbsLevel[ xC ][ yC ]       if( ( n = = firstSigScanPosSb ) && (sumAbsLevel % 2 ) = = 1 ) )        TransCoeffLevel[ x0 ][ y0 ][ cIdx ][xC ][ yC ] =          −TransCoeffLevel[ x0 ][ y0 ][ cIdx ][ xC ][ yC ]     }     }    }   }  } }

Referring to Table 19 as described above, if the value of theph_dep_quant_enabled_flag is 1, and the value of the transform_skip_flagis 0, the Qstate may be updated. For example, if the value of theph_dep_quant_enabled_flag is 1, and the value of the transform_skip_flagis 0, the Qstate may be updated asQStateTransTable[QState][AbsLevelPass1[xC][yC] & 1] orQStateTransTable[QState][AbsLevel[xC][yC] & 1]. Further, if the value ofthe transform_skip_flag is 1, the process of updating the Qstate may notbe performed.

Further, referring to Table 19 as described above, if the value of theph_dep_quant_enabled_flag is 1, and the value of the transform_skip_flagis 0, the Qstate may be derived, and the value of the transformcoefficient (transform coefficient level) may be derived based on theQState. For example, referring to Table 19, the transform coefficientlevel TransCoeffLevel[x0][y0][cIdx][xC][yC] may be derived as(2*AbsLevel[xC][yC]−(QState>1 ? 1:0))*(1−2*coeff_sign_flag[n]). Here,the AbsLevel[xC][yC] may be an absolute value of the transformcoefficient derived based on the syntax elements of the transformcoefficient, the coeff_sign_flag[n] may be the syntax element of thesign flag representing the sign of the transform coefficient, and the(QState>1 ? 1:0) may represent 1 if the value of the state QState islarger than 1, that is, if the value of the state Qstate is 2 or 3, andmay represent 0 if the value of the state Qstate is equal to or smallerthan 1, that is, if the value of the state Qstate is 0 or 1.

Further, referring to Table 19 as described above, if the value of thetransform_skip_flag is 1, the value of the transform coefficient(transform coefficient level) may be derived without using the Qstate.Accordingly, in case that the residual data according to the RRC iscoded for the transform skip block, the value of the transformcoefficient may be derived without using the Qstate. For example,referring to Table 19, the transform coefficient levelTransCoeffLevel[x0][y0][cIdx][xC][yC] may be derived asAbsLevel[xC][yC]*(1−2*coeff_sign_flag[n]). Here, the AbsLevel[xC][yC]may be an absolute value of the transform coefficient derived based onthe syntax elements of the transform coefficient, and thecoeff_sign_flag[n] may be the syntax element of the sign flagrepresenting the sign of the transform coefficient.

Further, for example, the present disclosure proposes an embodiment asshown in the following table.

TABLE 20 9.3.3.2 Rice parameter derivation process for abs_remainder[ ]and dec_abs_level[ ] Inputs to this process are the base levelbaseLevel, the colour component index cIdx, the luma location ( x0, y0 )specifying the top-left sample of the current transform block relativeto the top-left sample of the current picture, the current coefficientscan location ( xC, yC ), the binary logarithm of the transform blockwidth log2TbWidth, and the binary logarithm of the transform blockheight log2TbHeight. Output of this process is the Rice parametercRiceParam. Given the array AbsLevel[ x ][ y ] for the transform blockwith component index cIdx and the top-left luma location ( x0, y0 ), thevariable locSumAbs is derived as specified by the following pseudo code: locSumAbs = 0  if( xC < (1 << log2TbWidth) − 1 ) {   locSumAbs +=AbsLevel[ xC + 1 ][ yC ]   if( xC < (1 << log2TbWidth) − 2 )   locSumAbs += AbsLevel[ xC + 2 ][ yC ]   if( yC < (1 << log2TbHeight)− 1 )    locSumAbs += AbsLevel[ xC + 1 ][ yC + 1 ] (1.9-19)  }  if( yC <(1 << log2TbHeight) − 1 ) {   locSumAbs += AbsLevel[ xC ][ yC + 1 ]  if( yC < (1 << log2TbHeight) − 2 )    locSumAbs += AbsLevel[ xC ][yC + 2 ]  }  locSumAbs = Clip3( 0, 31, locSumAbs − baseLevel * 5 ) Giventhe variable locSumAbs, the Rice parameter cRiceParam is derived asspecified in Table 127. When baseLevel is equal to 0, the variableZeroPos[ n ] is derived as follows:   - If ph_dep_quant_enabled_flag isequal to 1 and transform_skip_flag is equal to 1,  ZeroPos[ n ] = 1 <<cRiceParam (1.9-20)   - Otherwise,  ZeroPos[ n ] = ( QState < 2 ? 1 : 2) << cRiceParam (1.9-21)

Referring to Table 20, a method of deriving ZeroPos of dec_abs_levelbased on ph_dep_quant_enabled_flag and transform_skip_flag may beselected. For example, when a value of ph_dep_quant_enabled_flag is 1and a value of transform_skip_flag is 1, ZeroPos of dec_abs_level may bederived based on an equation that does not use a state value ofdependent quantization. For example, as shown in Table 20 above, ZeroPosmay be derived as 1<<cRiceParam.

Meanwhile, for example, when the value of ph_dep_quant_enabled_flag is 0or the value of transform_skip_flag is 0, ZeroPos of dec_abs_level maybe derived depending on the state value of dependent quantization.

Further, the present disclosure proposes various embodiments related tosignalling of the above-described syntax elementsh_ts_residual_coding_disabled_flag.

For example, as described above, the sh_ts_residual_coding_disabled_flagis a syntax element defining whether the TSRC is not enabled, and incase that the transform skip block is not used, it may not be necessaryto be signaled. That is, only in case that the syntax element forwhether the transform skip block is used represents that the transformskip block is used, it may be significant to perform signaling of thesh_ts_residual_coding_disabled_flag.

Accordingly, the present disclosure proposes an embodiment for signalingthe sh_ts_residual_coding_disabled_flag only in case that thesps_transform_skip_enabled_flag is 1. The syntax according to thepresent embodiment is as in the following table.

TABLE 21 Descriptor slice_header( ) {  (...)  if(sps_transform_skip_enabled_flag)  slice_ts_residual_coding_disabled_flag u(1)  (...) }

Referring to Table 21, if the sps_transform_skip_enabled_flag is 1, thesh_ts_residual_coding_disabled_flag may be signaled, whereas if thesps_transform_skip_enabled_flag is 0, thesh_ts_residual_coding_disabled_flag may not be signaled. Here, forexample, the sps_transform_skip_enabled_flag may represent whether thetransform skip block is used. That is, for example, thesps_transform_skip_enabled_flag may represent whether the transform skipis enabled. For example, if the value of thesps_transform_skip_enabled_flag is 1, thesps_transform_skip_enabled_flag may represent that thetransform_skip_flag (transform_skip_flag) may be present in thetransform unit syntax, whereas if the value of thesps_transform_skip_enabled_flag is 0, thesps_transform_skip_enabled_flag may represent that the transform skipflag is not present in the transform unit syntax. Meanwhile, if thesh_ts_residual_coding_disabled_flag is not signaled, it may be inferredthat the sh_ts_residual_coding_disabled_flag is 0. Further, theabove-described sps_transform_skip_enabled_flag may be signaled in theSPS, or may be signaled in other high-level syntaxes (VPS, PPS, pictureheader syntax, and slice header syntax) being not the SPS, or low-levelsyntaxes (slice data syntax, coding unit syntax, and transform unitsyntax). Further, it may be signaled prior to theslice_ts_residual_coding_disabled_flag.

Further, the present disclosure proposes an embodiment in which theabove-described embodiments are combined in relation to the signaling ofthe sh_ts_residual_coding_disabled_flag. For example, as in thefollowing table, an embodiment for signalling thesh_ts_residual_coding_disabled_flag may be proposed.

TABLE 22 Descriptor slice_header( ) {  (...)  if(!ph_dep_quant_enabled_flag ||   sps_transform_skip_enabled_flag)  slice_ts_residual_coding_disabled_flag u(1)  (...) }

Referring to Table 22, in case that the sps_transform_skip_enabled_flagis 1, or the ph_dep_quant_enabled_flag is 0, thesh_ts_residual_coding_disabled_flag may be signaled, and otherwise, thesh_ts_residual_coding_disabled_flag may not be signaled. Meanwhile, incase that the sh_ts_residual_coding_disabled_flag is not signaled, thesh_ts_residual_coding_disabled_flag may be inferred as 0.

Further, for example, an embodiment for signaling thesh_ts_residual_coding_disabled_flag as in the following table may beproposed.

TABLE 23 Descriptor picture_header_structure( ) {  (...)  ph_dep_quant_enabled_flag   if(!ph_dep_quant_enabled_flag &&  sps_transform_skip_enabled_flag)   ph_ts_residual_coding_disabled_flagu(1)  (...) }

Referring to Table 23, the sh_ts_residual_coding_disabled_flag may besignaled to a picture header. The sh_ts_residual_coding_disabled_flagmay be represented as the ph_ts_residual_coding_disabled_flag. Further,referring to Table 23, the ph_dep_quant_enabled_flag may be signaled tothe picture header.

For example, referring to Table 23, in case that theph_dep_quant_enabled_flag is 0, and the sps_transform_skip_enabled_flagis 1, the ph_ts_residual_coding_disabled_flag may be signaled, andotherwise, the ph_ts_residual_coding_disabled_flag may not be signaled.Meanwhile, in case that the ph_ts_residual_coding_disabled_flag is notsignaled, the ph_ts_residual_coding_disabled_flag may be inferred as 0.

In the existing video/image coding standard in relation to syntaxelements described in the embodiments of the present disclosure, theph_dep_quant_enabled_flag may be signaled in the picture header syntax,and the sh_ts_residual_coding_disabled_flag may be signaled in the sliceheader syntax. In relation to this, the present disclosure proposes anembodiment for signaling two syntax elements in the same high-levelsyntax or low-level syntax.

For example, an embodiment may be proposed, in which both theph_dep_quant_enabled_flag and the sh_ts_residual_coding_disabled_flagare signaled in the picture header syntax. In this case, thesh_ts_residual_coding_disabled_flag may be called theph_ts_residual_coding_disabled_flag.

Further, for example, an embodiment may be proposed, in which both theph_dep_quant_enabled_flag and the sh_ts_residual_coding_disabled_flagare signaled in the slice header syntax. In this case, theph_dep_quant_enabled_flag may be called the sh_dep_quant_enabled_flag,sh_dep_quant_used_flag, or slice_dep_quant_enabled_flag.

Further, for example, an embodiment may be proposed, in which both theph_dep_quant_enabled_flag and the ph_ts_residual_coding_disabled_flagare signaled in the same HLS, but theph_ts_residual_coding_disabled_flag is signaled only in case that thevalue of the ph_dep_quant_enabled_flag is 0. For example, an example inwhich both the ph_dep_quant_enabled_flag and theph_ts_residual_coding_disabled_flag are signaled in the picture headersyntax may be as in the following table.

TABLE 24 Descriptor picture_header_structure( ) {  (...)  ph_dep_quant_enabled_flag   if(!ph_dep_quant_enabled_flag)  ph_ts_residual_coding_disabled_flag u(1)  (...) }

Referring to Table 24, the ph_dep_quant_enabled_flag may be signaled inthe picture header syntax, and if the value of theph_dep_quant_enabled_flag is 0, the ph_ts_residual_coding_disabled_flagmay be signaled in the picture header syntax, whereas if the value ofthe ph_dep_quant_enabled_flag is 1, theph_ts_residual_coding_disabled_flag may not be signaled. For example, ifthe ph_ts_residual_coding_disabled_flag is not signaled, theph_ts_residual_coding_disabled_flag may be inferred as 0.

Meanwhile, the above-described embodiment is an example, and an examplemay be proposed, in which the ph_dep_quant_enabled_flag and theph_ts_residual_coding_disabled_flag are signaled in other high-levelsyntaxes (VPS, SPS, PPS, and slice header syntax) or low-level syntaxes(slice data syntax, coding unit syntax, and transform unit syntax)rather than the picture header syntax.

Further, for example, an embodiment may be proposed, in which both theph_ts_residual_coding_disabled_flag and the ph_dep_quant_enabled_flagare signaled in the same HLS, but the ph_dep_quant_enabled_flag issignaled only in case that the value of theph_ts_residual_coding_disabled_flag is 0.

TABLE 25 Descriptor picture_header_structure( ) {  (...)  ph_ts_residual_coding_disabled_flag  if(!ph_ts_residual_coding_disabled_flag)   ph_dep_quant_enabled_flagu(1)  (...) }

Referring to Table 25, the ph_ts_residual_coding_disabled_flag may besignaled in the picture header syntax, and if the value of theph_ts_residual_coding_disabled_flag is 0, the ph_dep_quant_enabled_flagmay be signaled in the picture header syntax, whereas if the value ofthe ph_ts_residual_coding_disabled_flag is 1, theph_dep_quant_enabled_flag may not be signaled. For example, if theph_dep_quant_enabled_flag is not signaled, the ph_dep_quant_enabled_flagmay be inferred as 0.

Meanwhile, the above-described embodiment is an example, and an examplemay be proposed, in which the ph_ts_residual_coding_disabled_flag andthe ph_dep_quant_enabled_flag are signaled in other high-level syntaxes(VPS, SPS, PPS, and slice header syntax) or low-level syntaxes (slicedata syntax, coding unit syntax, and transform unit syntax) rather thanthe picture header syntax.

Further, for example, an embodiment in which the above-describedembodiments are combined with each other may be proposed. For example,an embodiment may be proposed, in which both theph_dep_quant_enabled_flag and the ph_ts_residual_coding_disabled_flagare signaled in the same HLS, but theph_ts_residual_coding_disabled_flag is signaled only in case that thevalue of the ph_dep_quant_enabled_flag is 0, or the value of thesps_transform_skip_enabled_flag is 1.

TABLE 26 Descriptor picture_header_structure( ) {  (...)  ph_dep_quant_enabled_flag   if(!ph_dep_quant_enabled_flag ||  sps_transform_skip_enabled_flag)   ph_ts_residual_coding_disabled_flagu(1)  (...) }

Referring to Table 26, the ph_dep_quant_enabled_flag may be signaled inthe picture header syntax, and in case that the value of theph_dep_quant_enabled_flag is 0, or the value of thesps_transform_skip_enabled_flag is 1, theph_ts_residual_coding_disabled_flag may be signaled in the pictureheader syntax, and otherwise, the ph_ts_residual_coding_disabled_flagmay not be signaled. Here, for example, thesps_transform_skip_enabled_flag may represent whether the transform skipblock is used. That is, for example, the sps_transform_skip_enabled_flagmay represent whether the transform skip is enabled. For example, if thevalue of the sps_transform_skip_enabled_flag is 1, thesps_transform_skip_enabled_flag may represent that thetransform_skip_flag (transform_skip_flag) may be present in thetransform unit syntax, whereas if the value of thesps_transform_skip_enabled_flag is 0, thesps_transform_skip_enabled_flag may represent that thetransform_skip_flag is not present in the transform unit syntax. Forexample, if the ph_ts_residual_coding_disabled_flag is not signaled, theph_ts_residual_coding_disabled_flag may be inferred as 0.

Further, for example, an embodiment may be proposed, in which both theph_dep_quant_enabled_flag and the ph_ts_residual_coding_disabled_flagare signaled in the same HLS (e.g., slice header syntax or the like),but the ph_ts_residual_coding_disabled_flag is signaled only in casethat the value of the ph_dep_quant_enabled_flag is 0, and the value ofthe sps_transform_skip_enabled_flag is 1.

TABLE 27 Descriptor picture_header_structure( ) {  (...)  ph_dep_quant_enabled_flag   if(!ph_dep_quant_enabled_flag &&  sps_transform_skip_enabled_flag)   ph_ts_residual_coding_disabled_flagu(1)  (...) }

Referring to Table 27, the ph_dep_quant_enabled_flag may be signaled inthe picture header syntax, and in case that the value of theph_dep_quant_enabled_flag is 0, and the value of thesps_transform_skip_enabled_flag is 1, theph_ts_residual_coding_disabled_flag may be signaled in the pictureheader syntax, and otherwise, the ph_ts_residual_coding_disabled_flagmay not be signaled. For example, if theph_ts_residual_coding_disabled_flag is not signaled, theph_ts_residual_coding_disabled_flag may be inferred as 0.

Further, for example, an embodiment may be proposed, in which both theph_dep_quant_enabled_flag and the ph_ts_residual_coding_disabled_flagare signaled in the same HLS, but theph_ts_residual_coding_disabled_flag is signaled only in case that thevalue of the sps_transform_skip_enabled_flag is 1, and theph_dep_quant_enabled_flag is signaled only in case that the value of theph_ts_residual_coding_disabled_flag is 0.

TABLE 28 Descriptor picture_header_structure( ) {  (...)  if(sps_transform_skip_enabled_flag)   ph_ts_residual_coding_disabled_flag  if(!ph_ts_residual_coding_disabled_flag)   ph_dep_quant_enabled_flagu(1)  (...) }

Referring to Table 28, if the value of thesps_transform_skip_enabled_flag is 1, theph_ts_residual_coding_disabled_flag may be signaled in the pictureheader syntax, whereas if the value of theph_ts_residual_coding_disabled_flag is 0, the ph_dep_quant_enabled_flagmay be signaled in the picture header syntax. For example, if the valueof the sps_transform_skip_enabled_flag is 0, theph_ts_residual_coding_disabled_flag may not be signaled. For example, ifthe ph_ts_residual_coding_disabled_flag is not signaled, theph_ts_residual_coding_disabled_flag may be inferred as 0. Further, forexample, if the value of the ph_ts_residual_coding_disabled_flag is 1,the ph_dep_quant_enabled_flag may not be signaled. For example, if theph_dep_quant_enabled_flag is not signaled, the ph_dep_quant_enabled_flagmay be inferred as 0,

Meanwhile, as described above, information (syntax elements) in a syntaxtable disclosed in the present disclosure may be included in image/videoinformation, configured/encoded by the encoding apparatus, andtransferred to the decoding apparatus in the form of a bitstream. Adecoding apparatus may parse/decode the information (syntax elements) inthe corresponding syntax table. The decoding apparatus may performblock/image/video reconstruction procedure based on the decodedinformation.

Further, the present disclosure proposes various embodiments related tosignaling of the above-described syntax elementsh_ts_residual_coding_disabled_flag.

For example, high coding efficiency can be obtained in a specificapplication (eg, lossless coding, etc.) by using theslice_ts_residual_coding_disabled_flag as described above, but in theexisting video/image coding standard, a constraint on the case whereslice_ts_residual_coding_disabled_flag is used together for sign datahiding (SDH) is not proposed.

Here, the sign data hiding method may be as follows. In deriving thetransform coefficient, the sign of the transform coefficient may bederived based on a 1-bit sign flag (the above-described syntax elementcoeff_sign_flag). In this regard, SDH may indicate a technique foromitting explicit signaling of coeff_sign_flag for a first significanttransform coefficient in a sub-block/coefficient group (CG) in order toimprove coding efficiency. Here, the value of coeff_sign_flag for thefirst significant transform coefficient may be derived based on the sumof absolute levels (ie, absolute values) of significant transformcoefficients in the corresponding sub-block/coefficient group. That is,the sign of the first significant transform coefficient may be derivedbased on the sum of absolute levels of the significant transformcoefficients in the corresponding sub-block/coefficient group.Meanwhile, the significant transform coefficient may mean a non-zerotransform coefficient whose (absolute) value is not 0. For example, whenthe sum of absolute levels for the significant transform coefficients iseven, the value of coeff_sign_flag for the first significant transformcoefficient may be derived as 1, and when the sum of absolute levels forthe significant transform coefficients is an odd, the value ofcoeff_sign_flag for the first significant transform coefficient may bederived as 0. In other words, for example, when the sum of absolutelevels for the significant transform coefficients is even, the value ofcoeff_sign_flag for the first significant transform coefficient may bederived as a negative value, and when the sum of absolute levels for thesignificant transform coefficients is an odd, the value ofcoeff_sign_flag for the first significant transform coefficient may bederived as a positive value. Or, for example, when the sum of absolutelevels for the significant transform coefficients is even, the value ofcoeff_sign_flag for the first significant transform coefficient may bederived as 0, and when the sum of absolute levels for the significanttransform coefficients is an odd, the value of coeff_sign_flag for thefirst significant transform coefficient may be derived as 1. In otherwords, for example, when the sum of absolute levels for the significanttransform coefficients is even, the value of coeff_sign_flag for thefirst significant transform coefficient may be derived as a positivevalue, and when the sum of absolute levels for the significant transformcoefficients is an odd, the value of coeff_sign_flag for the firstsignificant transform coefficient may be derived as a negative value.

For example, the SDH in the residual syntax may be as shown in thefollowing table.

TABLE 29 } signHiddenFlag = sh_sign_data_hiding_used_flag &&   (lastSigScanPosSb − firstSigScanPosSb > 3 ? 1 : 0 ) for( n = numSbCoeff −1; n >= 0; n− − ) {  xC = ( xS << log2SbW ) +  DiagScanOrder[ log2SbW ][log2SbH ][ n ][ 0 ]  yC = ( yS << log2SbH ) +  DiagScanOrder[ log2SbW ][log2SbH ][ n ][ 1 ]  if( ( AbsLevel[ xC ][ yC ] > 0 ) &&   (!signHiddenFlag | | ( n != firstSigScanPosSb ) ) )   coeff_sign_flag[ n] ae(v)

Referring to Table 29, the variable signHiddenFlag may indicate whetherthe SDH is applied. The variable signHiddenFlag may be calledsignHidden. For example, when a value of the variable signHiddenFlag is0, the variable signHiddenFlag may indicate that the SDH is not applied,and when the value of the variable signHiddenFlag is 1, the variablesignHiddenFlag may indicate that the SDH is applied. For example, thevalue of the variable signHiddenFlag may be set based on signaled flaginformation (eg, sh_sign_data_hiding_used_flag orpic_sign_data_hiding_enabled_flag or sps_sign_data_hiding_enabled_flag).Also, for example, the value of the variable signHiddenFlag may be setbased on lastSigScanPosSb and firstSigScanPosSb. Here, lastSigScanPosSbmay indicate a position of the last significant transform coefficientsearched in the corresponding sub-block/coefficient group according tothe scan order, and firstSigScanPosSb may indicate a position of thefirst significant transform coefficient searched in the correspondingsub-block/coefficient group according to the scan order. In general,lastSigScanPosSb may be located in a relatively high frequency componentregion than firstSigScanPosSb. Accordingly, whenlastSigScanPosSb−firstSigScanPosSb is greater than a predeterminedthreshold, the signHidden value may be derived as 1 (ie, SDH isapplied), otherwise, the signHidden value may be derived as 0 (ie, SDHis not applied). Here, for example, referring to Table 29, the thresholdmay be set to 3.

Meanwhile, when the sign data hiding is activated in high-level syntax(VPS, SPS, PPS, slice header syntax, etc.) or low-level syntax (slicedata syntax, coding unit syntax, transform unit syntax, etc.), and theslice_ts_residual_coding_disabled_flag is 1, the sign data hidingprocess of RRC can be used in lossless coding. Accordingly, losslesscoding may become impossible due to incorrect settings in the encodingapparatus. Alternatively, when loss coding (ie, an irreversible codingmethod) other than lossless coding is applied, and a residual signal towhich transform skip is applied is coded with RRC and BDPCM is appliedat the same time, although the interval in which the residual valuebecomes 0 occurs more frequently than in the general case due to thedifference between the residuals in BDPCM, coding loss may occur becauseSDH is performed in accordance with the SDH application condition.Specifically, for example, when significant transform coefficients(non-zero residual data) exist at positions 0 and 15 in the CG,respectively, and the value of the transform coefficients at theremaining positions in the CG is 0, SDH may be applied to the CGaccording to the above-described SDH application condition, and thus,sign data (ie, coding of a sign flag) for the first significanttransform coefficient of the CG may be omitted. Accordingly, in thiscase, the parity of only two residual data of the CG may be adjusted inthe quantization step to omit the sign data, and rather than the casewhere SDH is not applied, more coding loss may occur. Such a case mayoccur even in blocks to which BDPCM is not applied, but due to thecharacteristics of BDPCM, the level is lowered through the differencewith the neighboring residual, so disadvantageous cases may occur morefrequently in applying SDH.

Therefore, in order to prevent SDH and residual coding ofslice_ts_residual_coding_disabled_flag=1 (that is, coding the residualsamples of the transform skip block in the current slice with RRC) frombeing used together to cause unintended coding loss or malfunction, thepresent disclosure proposes an embodiment for settingdependency/constraint between two technologies.

For example, the present disclosure proposes a method in whichslice_ts_residual_coding_disabled_flag is dependent onpic_sign_data_hiding_enabled_flag. The residual coding syntax accordingto the present embodiment may be as shown in the following table.

TABLE 30 Descriptor slice_header( ) { picture_header_in_slice_header_flag u(1)  if(picture_header_in_slice_header_flag )   picture_header_structure( ) (...)  if(!pic_sign_data_hiding_enabled_flag) slice_ts_residual_coding_disabled_flag u(1)  if( ph_lmcs_enabled_flag )  slice_lmcs_enabled_flag u(1)  if( pic_scaling_list_enabled_flag )  slice_scaling_list_present_flag u(1)  if( NumEntryPoints > 0 ) {  offset_len_minus1 ue(v)   for( i = 0; i < NumEntryPoints; i++ )   entry_point_offset_minus1[ i ] u(v)  }  if(slice_header_extension_present_flag ) {   slice_header_extension_lengthue(v)   for( i = 0; i < slice_header_extension_length; i++)   slice_header_extension_data_byte[ i ] u(8)  }  byte_alignment( ) }

Here, slice_ts_residual_coding_disabled_flag may be signaled as a sliceheader syntax, or a High Level Syntax (HLS) other than the slice headersyntax (eg, SPS syntax/DPS syntax/DPS syntax, etc.), or low level(CU/TU). In addition, pic_sign_data_hiding_enabled_flag may be signaledin picture header syntax, or other high-level syntax (HLS) other thanthe picture header syntax (eg, SPS syntax/VPS syntax/DPS syntax, etc.),or low-level (CU/TU). For example, whenpic_sign_data_hiding_enabled_flag is signaled in a syntax other than thepicture header syntax, it may be called another name. For example, thepic_sign_data_hiding_enabled_flag may be represented bysps_sign_data_hiding_enabled_flag.

Also, sps_sign_data_hiding_enabled_flag may be a flag indicating whethersign data hiding is enabled. That is, for example,sps_sign_data_hiding_enabled_flag may indicate whether the sign datahiding is enabled. For example, when the value ofsps_sign_data_hiding_enabled_flag is 1,sps_sign_data_hiding_enabled_flag may indicate that the sign data hidingis enabled, and when the value of sps_sign_data_hiding_enabled_flag is0, sps_sign_data_hiding_enabled_flag may indicate that the sign datahiding is not enabled.

According to Table 30 disclosing the present embodiment,slice_ts_residual_coding_disabled_flag may be signaled only when signdata hiding is not enabled. In addition, when sign data hiding isenabled, slice_ts_residual_coding_disabled_flag may not be signaled, avalue of slice_ts_residual_coding_disabled_flag may be inferred as 0(coding the residual sample of the transform skip block in the currentslice with TSRC syntax) or 1 (coding the residual sample of thetransform skip block in the current slice with RRC syntax).

Further, the present disclosure proposes an embodiment in which theabove-described embodiments are combined with respect to signaling ofsh_ts_residual_coding_disabled_flag. For example, an embodimentsignaling sh_ts_residual_coding_disabled_flag may be proposed as shownin the following table.

TABLE 31 Descriptor slice_header( ) { picture_header_in_slice_header_flag u(1)  if(picture_header_in_slice_header_flag )   picture_header_structure( ) (...)  if(sps_transform_skip_enabled_flag && !ph_dep_quant_enabled_flag && !pi c_sign_data_hiding_enabled_flag) slice_ts_residual_coding_disabled_flag u(1)  if( ph_lmcs_enabled_flag )  slice_lmcs_enabled_flag u(1)  if( pic_scaling_list_enabled_flag )  slice_scaling_list_present_flag u(1)  if( NumEntryPoints > 0 ) {  offset_len_minus1 ue(v)   for( i = 0; i < NumEntryPoints; i++ )   entry_point_offset_minus1[ i ] u(v)  }  if(slice_header_extension_present_flag ) {   slice_header_extension_lengthue(v)   for( i = 0; i < slice_header_extension_length; i++)   slice_header_extension_data_byte[ i ] u(8)  }  byte_alignment( ) }

Referring to Table 31, when sps_transform_skip_enabled_flag is 1,ph_dep_quant_enabled_flag is 0, and pic_sign_data_hiding_enabled_flag is0, sh_ts_residual_coding_disabled_disable_flag may be signaled, andotherwise, sh_is_residual_coding_disabled_disable_flag may not besignaled. On the other hand, when sh_ts_residual_coding_disabled_flag isnot signaled, sh_ts_residual_coding_disabled_flag may be inferred as 0.

Meanwhile, the embodiment of Table 31 is an example, and an example inwhich ph_dep_quant_enabled_flag, pic_sign_data_hiding_enabled_flag, andph_ts_residual_coding_disabled_flag are all signaled in the same HLS(eg, slice header syntax, etc.) may be proposed.

Alternatively, for example, an embodiment of signalingsh_ts_residual_coding_disabled_flag as shown in the following table maybe proposed.

TABLE 32 Descriptor slice_header( ) { picture_header_in_slice_header_flag u(1)  if(picture_header_in_slice_header_flag )   picture_header_structure( ) (...)  if(!ph_dep_quant_enabled_flag && !pic_sign_data_hiding_enabled_flag) slice_ts_residual_coding_disabled_flag u(1)  if( ph_lmcs_enabled_flag )  slice_lmcs_enabled_flag u(1)  if( pic_scaling_list_enabled_flag )  slice_scaling_list_present_flag u(1)  if( NumEntryPoints > 0 ) {  offset_len_minus1 ue(v)   for( i = 0; i < NumEntryPoints; i++ )   entry_point_offset_minus1[ i ] u(v)  }  if(slice_header_extension_present_flag ) {   slice_header_extension_lengthue(v)   for( i = 0; i < slice_header_extension_length; i++)   slice_header_extension_data_byte[ i ] u(8)  }  byte_alignment( ) }

Referring to Table 32, when ph_dep_quant_enabled_flag is 0 andpic_sign_data_hiding_enabled_flag is 0,sh_ts_residual_coding_disabled_flag may be signaled, and otherwise,sh_ts_residual_coding_disabled_flag may not be signaled. On the otherhand, when sh_ts_residual_coding_disabled_flag is not signaled,sh_ts_residual_coding_disabled_flag may be inferred as 0.

Meanwhile, the embodiment of Table 32 is an example, and an example inwhich ph_dep_quant_enabled_flag, pic_sign_data_hiding_enabled_flag, andph_ts_residual_coding_disabled_flag are all signaled in the same HLS(eg, slice header syntax, etc.) may be proposed.

Alternatively, for example, an embodiment of signalingsh_ts_residual_coding_disabled_flag as shown in the following table maybe proposed.

TABLE 33 Descriptor slice_header( ) { picture_header_in_slice_header_flag u(1)  if(picture_header_in_slice_header_flag )   picture_header_structure( ) (...)  if(!ph_dep_quant_enabled_flag || !pic_sign_data_hiding_enabled_flag) slice_ts_residual_coding_disabled_flag u(1)  if( ph_lmcs_enabled_flag )  slice_lmcs_enabled_flag u(1)  if( pic_scaling_list_enabled_flag )  slice_scaling_list_present_flag u(1)  if( NumEntryPoints > 0 ) {  offset_len_minus1 ue(v)   for( i = 0; i < NumEntryPoints; i++ )   entry_point_offset_minus1[ i ] u(v)  }  if(slice_header_extension_present_flag ) {   slice_header_extension_lengthue(v)   for( i = 0; i < slice_header_extension_length; i++)   slice_header_extension_data_byte[ i ] u(8)  }  byte_alignment( ) }

Referring to Table 33, when ph_dep_quant_enabled_flag is 0 orpic_sign_data_hiding_enabled_flag is 0,sh_ts_residual_coding_disabled_flag may be signaled, and otherwise,sh_ts_residual_coding_disabled_flag may not be signaled. On the otherhand, when sh_ts_residual_coding_disabled_flag is not signaled,sh_ts_residual_coding_disabled_flag may be inferred as 0.

In addition, the present disclosure proposes an embodiment in which theabove-described syntax elements ph_dep_quant_enabled_flag,pic_sign_data_hiding_enabled_flag andslice_ts_residual_coding_disabled_flag are signaled in the samehigh-level syntax or low-level syntax.

For example, an embodiment in which ph_dep_quant_enabled_flag,pic_sign_data_hiding_enabled_flag, andslice_ts_residual_coding_disabled_flag are all signaled in the pictureheader syntax may be proposed as shown in the following table.

TABLE 34 Descriptor picture_header_structure( ) {  (...) ph_ts_residual_coding_disabled_flag u(1) if(!ph_ts_residual_coding_disabled_flag){   if(sps_dep_quant_enabled_flag)  ph_dep_quant_enabled_flag u(1)   if(sps_sign_data_hiding_enabled_flag &&   !ph_dep_quant_enabled_flag)   pic_sign_data_hiding_enabled_flag u(1)  }  (...) }

In this case, slice_ts_residual_coding_disabled_flag may be referred toas ph_ts_residual_coding_disabled_flag.

Referring to Table 34, ph_ts_residual_coding_disabled_flag may besignaled in the picture header syntax, and when a value ofph_ts_residual_coding_disabled_flag is 0, if a value ofsps_dep_quant_enabled_flag is 1, ph_dep_quant_enabled_flag may besignaled in the picture header syntax. In addition, when the value ofph_ts_residual_coding_disabled_flag is 0, if the value ofsps_sign_data_hiding_enabled_flag is 1 and ph_dep_quant_enabled_flag is0, pic_sign_data_hiding_enabled_flag may be signaled in the pictureheader syntax. Meanwhile, for example, when the value ofph_ts_residual_coding_disabled_flag is 1, ph_dep_quant_enabled_flag andpic_sign_data_hiding_enabled_flag may not be signaled.

Alternatively, for example, an embodiment in whichph_dep_quant_enabled_flag, pic_sign_data_hiding_enabled_flag, andslice_ts_residual_coding_disabled_flag are all signaled in the pictureheader syntax as shown in the following table may be proposed.

TABLE 35 Descriptor picture_header_structure( ) {  (...) if(sps_transform_skip_enabled_flag)  ph_ts_residual_coding_disabled_flag u(1) if(!ph_ts_residual_coding_disabled_flag){   if(sps_dep_quant_enabled_flag)    ph_dep_quant_enabled_flag u(1)   if(sps_sign_data_hiding_enabled_flag &&   !ph_dep_quant_enabled_flag)   pic_sign_data_hiding_enabled_flag u(1)  }  (...) }

Referring to Table 35, when the value of sps_transform_skip_enabled_flagis 1, ph_ts_residual_coding_disabled_flag may be signaled in the pictureheader syntax. Also, for example, when the value ofsps_transform_skip_enabled_flag is 0,ph_ts_residual_coding_disabled_flag may not be signaled. Whenph_ts_residual_coding_disabled_flag is not signaled,ph_ts_residual_coding_disabled_flag may be inferred as 0 in the decodingapparatus.

Also, referring to Table 35, when the value ofph_ts_residual_coding_disabled_flag is 0 and the value ofsps_dep_quant_enabled_flag is 1, ph_dep_quant_enabled_flag may besignaled in the picture header syntax. In addition, when the value ofph_ts_residual_coding_disabled_flag is 0, if the value ofsps_sign_data_hiding_enabled_flag is 1 and ph_dep_quant_enabled_flag is0, pic_sign_data_hiding_enabled_flag may be signaled in the pictureheader syntax. Meanwhile, for example, when the value ofph_ts_residual_coding_disabled_flag is 1, ph_dep_quant_enabled_flag andpic_sign_data_hiding_enabled_flag may not be signaled. Also, forexample, when ph_dep_quant_enabled_flag is not signaled,ph_dep_quant_enabled_flag may be inferred as 0 in the decodingapparatus. Also, for example, when pic_sign_data_hiding_enabled_flag isnot signaled, pic_sign_data_hiding_enabled_flag may be inferred as 0 inthe decoding apparatus.

Meanwhile, the above-described embodiments are examples, an example inwhich ph_ts_residual_coding_disabled_flag, ph_dep_quant_enabled_flag andpic_sign_data_hiding_enabled_flag are signaled in a high-level syntax(VPS, SPS, PPS, slice header syntax, etc.) or low-level syntax (slicedata syntax, coding unit syntax, etc.) other than the picture headersyntax may be proposed.

Meanwhile, as described above, information (syntax element) in thesyntax table disclosed in the present disclosure may be included in theimage/video information, and may be configured/encoded in the encodingapparatus and transmitted to the decoding apparatus in the form of abitstream. The decoding apparatus may parse/decode information (syntaxelement) in the corresponding syntax table. The decoding apparatus mayperform a block/image/video reconstruction process based on the decodedinformation.

FIG. 14 briefly illustrates an image encoding method performed by anencoding apparatus according to the present disclosure. The methoddisclosed in FIG. 11 may be performed by the encoding apparatusdisclosed in FIG. 2 . Specifically, for example, S1100 of FIG. 11 may beperformed by the predictor of the encoding apparatus, S1110 of FIG. 11may be performed by the subtractor of the encoding apparatus, and S1120to S1140 of FIG. 14 may be performed by the entropy encoder of theencoding apparatus. Further, although not illustrated, a process ofgenerating a reconstructed sample and a reconstructed picture for thecurrent block based on the residual sample and the prediction sample forthe current block may be performed by the adder of the encodingapparatus.

The encoding apparatus encodes a dependent quantization enabled flag forwhether dependent quantization is enabled (S1400). The encodingapparatus may encode a dependent quantization enabled flag for whetherdependent quantization is enabled. The image information may include thedependent quantization enabled flag. For example, the encoding apparatusmay determine whether the dependent quantization is enabled for blocksof pictures in a sequence, and may encode the dependent quantizationenabled flag for whether the dependent quantization is enabled. Forexample, the dependent quantization enabled flag may be a flag forwhether the dependent quantization is enabled. For example, thedependent quantization enabled flag may represent whether the dependentquantization is enabled. That is, for example, the dependentquantization enabled flag may represent whether the dependentquantization is enabled for blocks of pictures in a sequence. Forexample, the dependent quantization enabled flag may represent whether adependent quantization used flag representing whether the dependentquantization is used for a current slice may be present. For example,the dependent quantization enabled flag having a value of 1 mayrepresent that the dependent quantization is enabled, and the dependentquantization enabled flag having a value of 0 may represent that thedependent quantization is not enabled. Also, for example, the dependentquantization enabled flag may be signaled in an SPS syntax or a sliceheader syntax. The syntax element of the dependent quantization enabledflag may be the above-described sps_dep_quant_enabled_flag. Thesps_dep_quant_enabled_flag may be referred to assh_dep_quant_enabled_flag, sh_dep_quant_used_flag, orph_dep_quant_enabled_flag.

The encoding apparatus encodes a sign data hiding enabled flag forwhether sign data hiding is enabled (S1410). The encoding apparatus mayencode a sign data hiding enabled flag for whether sign data hiding isenabled. The image information may include the sign data hiding enabledflag. For example, the encoding apparatus may determine whether the signdata hiding is enabled for blocks of pictures in a sequence, and mayencode the sign data hiding enabled flag for whether the sign datahiding is enabled. For example, the sign data hiding enabled flag may bea flag for whether the sign data hiding is enabled. For example, thesign data hiding enabled flag may represent whether the sign data hidingis enabled. That is, for example, the sign data hiding enabled flag mayrepresent whether the sign data hiding is enabled for blocks of picturesin a sequence. For example, the sign data hiding enabled flag mayrepresent whether a sign data hiding used flag representing whether thesign data hiding is used for a current slice may be present. Forexample, the sign data hiding enabled flag having a value of 1 mayrepresent that the sign data hiding is enabled, and the sign data hidingenabled flag having a value of 0 may represent that the sign data hidingis not enabled. For example, the sign data hiding enabled flag having avalue of 1 may represent that the sign data hiding used flag may bepresent, and the sign data hiding enabled flag having a value of 0 mayrepresent that the sign data hiding used flag is not present. Also, forexample, the sign data hiding enabled flag may be signaled in an SPSsyntax. Alternatively, for example, the sign data hiding enabled flagmay be signaled in a picture header syntax or a slice header syntax. Thesyntax element of the sign data hiding enabled flag may be thesps_sign_data_hiding_enabled_flag.

The encoding apparatus encodes a transform skip residual coding (TSRC)enabled flag for whether TSRC is enabled based on the dependentquantization enabled flag and the sign data hiding enabled flag (S1420).The image information may include the TSRC enabled flag.

For example, the encoding apparatus may encode the TSRC enabled flagbased on the dependent quantization enabled flag and the sign datahiding enabled flag. For example, the TSRC enabled flag may be encodedbased on the dependent quantization enabled flag having a value of 0 andthe sign data hiding enabled flag having a value of 0. That is, forexample, when a value of the dependent quantization enabled flag is 0(that is, the dependent quantization enabled flag represents that thedependent quantization is not enabled), and a value of the sign datahiding enabled flag is 0 (that is, the sign data hiding enabled flagrepresents that the sign data hiding is not enabled), the TSRC enabledflag may be encoded. In other words, for example, when a value of thedependent quantization enabled flag is 0 (that is, the dependentquantization enabled flag represents that the dependent quantization isnot enabled), and a value of the sign data hiding enabled flag is 0(that is, the sign data hiding enabled flag represents that the signdata hiding is not enabled), the TSRC enabled flag may be signaled.Also, for example, when the value of the sign data hiding enabled flagis 1, the TSRC enabled flag may not be encoded, and a value of the TSRCenabled flag may be derived as 0 in the decoding apparatus. That is, forexample, when the value of the sign data hiding enabled flag is 1, theTSRC enabled flag may not be signaled, and a value of the TSRC enabledflag may be derived as 0 in the decoding apparatus. Also, for example,when the value of the dependent quantization enabled flag is 1, the TSRCenabled flag may not be encoded, and a value of the TSRC enabled flagmay be derived as 0 in the decoding apparatus. That is, for example,when the value of the dependent quantization enabled flag is 1 (eg, whenthe dependent quantization is applied (or used) to the current block),the TSRC enabled flag may not be signaled, and a value of the TSRCenabled flag may be derived as 0 in the decoding apparatus. Thus, forexample, when the dependent quantization and the sign data hiding arenot enabled for the current block, the TSRC enabled flag may be signaled(or encoded). When the dependent quantization and/or sign data hiding isenabled for the current block, the TSRC enabled flag may not be signaled(or encoded), and the value of the TSRC enabled flag may be derived as 0in the decoding apparatus. Here, the current block may be a Coding Block(CB) or a Transform Block (TB).

Here, for example, the TSRC enabled flag may be a flag for whether theTSRC is enabled. That is, for example, the TSRC enabled flag may a flagrepresenting whether the TSRC is enabled for blocks in a slice. Forexample, the TSRC enabled flag having a value of 1 may represent thatthe TSRC is not enabled, and the TSRC enabled flag having a value of 0may represent that the TSRC is enabled. Also, for example, the TSRCenabled flag may be signaled in a slice header syntax. The syntaxelement of the TSRC enabled flag may be the above-describedsh_ts_residual_coding_disabled_flag.

Meanwhile, for example, the encoding apparatus may encode the transformskip enabled flag for whether the transform skip is enabled. Imageinformation may include the transform skip enabled flag. For example,the encoding apparatus may determine whether the transform skip isenabled for blocks of pictures in a sequence, and may encode thetransform skip enabled flag for whether the transform skip is enabled.For example, the transform skip enabled flag may be a flag for whetherthe transform skip is enabled. For example, the transform skip enabledflag may represent whether the transform skip is enabled. That is, forexample, the transform skip enabled flag may represent whether thetransform skip is enabled for the blocks of the pictures in thesequence. For example, the transform skip enabled flag may representwhether the transform skip flag can be present. For example, thetransform skip enabled flag having the value of 1 may represent that thetransform skip is enabled, and the transform skip enabled flag havingthe value of 0 may represent that the transform skip is not enabled.That is, for example, the transform skip enabled flag having the valueof 1 may represent that the transform_skip_flag can be present, and thetransform skip enabled flag having the value of 0 may represent that thetransform_skip_flag is not present. Further, for example, the transformskip enabled flag may be signaled to a sequence parameter set (SPS)syntax. The syntax element of the transform skip enabled flag may be theabove-described sps_transform_skip_enabled_flag.

Further, for example, the TSRC enabled flag may be encoded based on thesign data hiding enabled flag, the dependent quantization enabled flag,and/or the transform skip enabled flag. For example, the TSRC enabledflag may be encoded based on the sign data hiding enabled flag having avalue of 0, the dependent quantization enabled flag having a value of 0,and the transform skip enabled flag having a value of 1. That is, forexample, when a value of the sign data hiding enabled flag is 0 (thatis, the sign data hiding enabled flag represents that sign data hidingis not enabled), a value of the dependent quantization enabled flag is 0(that is, the dependent quantization enabled flag represents thatdependent quantization is not enabled), and a value of the transformskip enabled flag is 1 (that is, the transform skip enabled flagrepresents that transform skip is enabled), the TSRC The enabled flagmay be encoded (or signaled). Also, for example, when the value of thedependent quantization enabled flag is 1, the TSRC enabled flag may notbe encoded, and the value of the TSRC enabled flag may be derived as 0in the decoding apparatus. That is, for example, when the value of thedependent quantization enabled flag is 1, the TSRC enabled flag may notbe signaled, and the value of the TSRC enabled flag may be derived as 0in the decoding apparatus. Also, for example, when the value of thetransform skip enabled flag is 0, the TSRC enabled flag may not beencoded, and the value of the TSRC enabled flag may be derived as 0.That is, for example, when the value of the transform skip enabled flagis 0, the TSRC enabled flag may not be signaled, and the value of theTSRC enabled flag may be derived as 0.

The encoding apparatus encodes residual information for a current blockbased on the TSRC enabled flag (S1430). The encoding apparatus mayencode residual information for a current block based on the TSRCenabled flag.

For example, the encoding apparatus may determine a residual codingsyntax for the current block based on the TSRC enabled flag. Forexample, the encoding apparatus may determine the residual coding syntaxfor the current block as one of a regular residual coding (RRC) syntaxand a transform skip residual coding (TSRC) syntax based on the TSRCenabled flag. The RRC syntax may represent a syntax according to RRC,and the TSRC syntax may represent a syntax according to the TSRC.

For example, based on the TSRC enabled flag having the value of 1, theresidual coding syntax for the current block may be determined as theregular residual coding (RRC) syntax. In this case, for example, thetransform skip flag for whether the current block is the transform skipblock may be encoded, and the value of the transform skip flag may be 1.For example, the image information may include the transform skip flagfor the current block. The transform skip flag may represent whether thecurrent block is the transform skip block. That is, the transform skipflag may represent whether the transform has been applied to thetransform coefficients of the current block. The syntax elementrepresenting the transform skip flag may be the transform_skip_flag asdescribed above. For example, if the value of the transform skip flag is1, the transform skip flag may represent that the transform has not beenapplied to the current block (i.e., transform skipped), whereas if thevalue of the transform skip flag is 0, the transform skip flag mayrepresent that the transform has been applied to the current block. Forexample, if the current block is the transform skip block, the value ofthe transform skip flag for the current block may be 1.

Further, for example, based on the TSRC enabled flag having the value of0, the residual coding syntax for the current block may be determined asthe transform skip residual coding (TSRC) syntax. Further, for example,the transform skip flag for whether the current block is the transformskip block may be encoded, and based on the transform skip flag havingthe value of 1 and the TSRC enabled flag having the value of 0, theresidual coding syntax for the current block may be determined as thetransform skip residual coding (TSRC) syntax. Further, for example, thetransform skip flag for whether the current block is the transform skipblock may be encoded, and based on the transform skip flag having thevalue of 0 and the TSRC enabled flag having the value of 0, the residualcoding syntax for the current block may be determined as the regularresidual coding (RRC) syntax.

Thereafter, for example, the encoding apparatus may encode the residualinformation of the determined residual coding syntax for the currentblock. The encoding apparatus may derive a residual sample for thecurrent block, and may encode residual information of the determinedresidual coding syntax for the residual sample of the current block. Forexample, residual information of the regular residual coding (RRC)syntax may be encoded based on the TSRC enabled flag having the value of1, and residual information of the TSRC syntax may be encoded based onthe TSRC enabled flag having the value of 0. The image information mayinclude the residual information.

For example, the encoding apparatus may determine whether to performinter prediction or intra prediction on the current block, and maydetermine a specific inter prediction mode or a specific intraprediction mode based on the RD cost. According to the determined mode,the encoding apparatus may derive prediction samples for the currentblock, and may derive residual samples for the current block bysubtracting the prediction samples from the original samples for thecurrent block.

Then, for example, the encoding apparatus may derive the transformcoefficients of the current block based on the residual samples. Forexample, the encoding apparatus may determine whether the transform isapplied for the current block. That is, the encoding apparatus maydetermine whether the transform is applied for the residual samples ofthe current block. The encoding apparatus may determine whether thetransform is applied for the current block in consideration of thecoding efficiency. For example, the encoding apparatus may determinethat the transform is not applied for the current block. The block towhich the transform is not applied may be represented as the transformskip block. That is, for example, the current block may be the transformskip block.

If the transform is not applied for the current block, that is, if thetransform is not applied for the residual samples, the encodingapparatus may derive the derived residual samples as the currenttransform coefficients. Further, if the transform is applied for thecurrent block, that is, if the transform is applied for the residualsamples, the encoding apparatus may derive the transform coefficients byperforming the transform for the residual samples. The current block mayinclude a plurality of subblocks or coefficient groups (CGs). Further,the size of the subblock of the current block may be a 4×4 size or a 2×2size. That is, the subblock of the current block may maximally include16 non-zero transform coefficients or 4 non-zero transform coefficients.Here, the current block may be the coding block (CB) or the transformblock (TB). Further, the transform coefficient may be represented as theresidual coefficient.

Meanwhile, the encoding apparatus may determine whether the dependentquantization is applied for the current block. For example, if thedependent quantization is applied for the current block, the encodingapparatus may derive the transform coefficients of the current block byperforming the dependent quantization process for the transformcoefficients. For example, if the dependent quantization is applied forthe current block, the encoding apparatus may update the state (Qstate)for the dependent quantization based on the coefficient level of thetransform coefficient just before the current transform coefficient inthe scanning order, may derive the coefficient level of the currenttransform coefficient based on the updated state and the syntax elementsfor the current transform coefficient, and may derive the currenttransform coefficient by quantizing the derived coefficient level. Forexample, the current transform coefficient may be quantized based on thequantization parameter for the reconstructed level of the currenttransform coefficient in a scalar quantizer for the updated state.

For example, if the residual coding syntax for the current block isdetermined as the RRC syntax, the encoding apparatus may encode theresidual information of the RRC syntax for the current block. Forexample, the residual information of the RRC syntax may include thesyntax elements disclosed in Table 2 as described above.

For example, the residual information of the RRC syntax may include thesyntax elements for the transform coefficient of the current block.Here, the transform coefficient may be represented as the residualcoefficient.

For example, the syntax elements may include syntax elements, such aslast_sig_coeff_x_prefix, last_sig_coeff_y_prefix,last_sig_coeff_x_suffix, last_sig_coeff_y_suffix, sb_coded_flag,sig_coeff_flag, par_level_flag, abs_level_gtX_flag (e.g.,abs_level_gtx_flag[n][0] and/or abs_level_gtx_flag[n][1]),abs_remainder, dec_abs_level, and/or coeff_sign_flag.

Specifically, for example, the syntax elements may include positioninformation representing the position of the last non-zero transformcoefficient in a residual coefficient array of the current block. Thatis, the syntax elements may include the position informationrepresenting the position of the last non-zero transform coefficient inthe scanning order of the current block. The position information mayinclude information representing a prefix in a column position of thelast non-zero transform coefficient, information representing a prefixin a row position of the last non-zero transform coefficient,information representing a suffix of the column position of the lastnon-zero transform coefficient, and information representing a suffix inthe row position of the last non-zero transform coefficient. The syntaxelements for the position information may be last_sig_coeff_x_prefix,last_sig_coeff_y_prefix, last_sig_coeff_x_suffix, andlast_sig_coeff_y_suffix. Meanwhile, the non-zero transform coefficientmay be called a significant coefficient.

Further, for example, the syntax elements may include a coded subblockflag representing whether the current subblock of the current blockincludes the non-zero transform coefficient, a significant coefficientflag representing whether the transform coefficient of the current blockis the non-zero transform coefficient, a first coefficient level flagfor whether the coefficient level for the transform coefficient islarger than a first threshold value, a parity level flag for a parity ofthe coefficient level, and/or a second coefficient level flag forwhether the coefficient level of the transform coefficient is largerthan a second threshold value. Here, the coded subblock flag may be thesb_coded_flag or coded_sub_block_flag, the significant coefficient flagmay be the sig_coeff_flag, the first coefficient level flag may be theabs_level_gt1_flag or the abs_level_gtx_flag, the parity level flag maybe the par_level_flag, and the second coefficient level flag may be theabs_level_gt3_flag or the abs_level_gtx_flag.

Further, for example, the syntax elements may include coefficient valuerelated information for the transform coefficient value of the currentblock. The coefficient value related information may be an abs_remainderand/or a dec_abs_level.

Further, for example, the syntax elements may include a sign flagrepresenting the sign of the transform coefficient. The sign flag may bethe coeff_sign_flag.

Meanwhile, for example, when the sign data hiding is applied to thecurrent block, a sign flag of a first significant transform coefficientof a current coefficient group (CG) in the current block may be notencoded and signaled. That is, for example, when the sign data hiding isapplied to the current block, the syntax elements may not include a signflag representing a sign of the first significant transform coefficient.Meanwhile, for example, whether the sign data hiding is applied to thecurrent block may be derived based on the sign data hiding enabled flagand/or a position of the first significant transform coefficient and aposition of the last significant transform coefficient of the currentCG. For example, when a value of the sign data hiding enabled flag is 1,and a value obtained by subtracting the position of the firstsignificant transform coefficient from the position of the lastsignificant transform coefficient is greater than 3, (that is, when avalue of the sign data hiding enabled flag is 1, and a number ofsignificant transform coefficients in the current CG is greater than 3),the sign data hiding may be applied to the current CG of the currentblock.

Further, for example, if the residual coding syntax for the currentblock is determined as the TSRC syntax, the encoding apparatus mayencode the residual information of the TSRC syntax for the currentblock. For example, the residual information of the TSRC syntax mayinclude the syntax elements disclosed in Table 3 as described above.

For example, the residual information of the TSRC syntax may include thesyntax elements for the transform coefficient of the current block.Here, the transform coefficient may be represented as the residualcoefficient.

For example, the syntax elements may include context-coded syntaxelements for the transform coefficient and/or bypass-coded syntaxelements. The syntax elements may include the syntax elements, such assig_coeff_flag, coeff_sign_flag, par_level_flag, abs_level_gtX_flag(e.g., abs_level_gtx_flag[n][0], abs_level_gtx_flag[n][1],abs_level_gtx_flag[n][2], abs_level_gtx_flag[n][3], and/orabs_level_gtx_flag[n][4]), abs_remainder, and/or coeff_sign_flag.

For example, the context-coded syntax elements for the transformcoefficient may include a significant coefficient flag representingwhether the transform coefficient is the non-zero transform coefficient,a sign flag representing the sign for the transform coefficient, a firstcoefficient level flag for whether the coefficient level for thetransform coefficient is larger than a first threshold value, and/or aparity level flag for the parity of the transform level for thetransform coefficient. Further, for example, the context-coded syntaxelements may include a second coefficient level flag for whether thecoefficient level of the transform coefficient Further, for example, thecontext-coded syntax elements may include a second coefficient levelflag for whether the coefficient level of the transform coefficient islarger than a second threshold value, a third coefficient level flag forwhether the coefficient level of the transform coefficient is largerthan a third threshold value, a fourth coefficient level flag forwhether the coefficient level of the transform coefficient is largerthan a fourth threshold value, and/or a fifth coefficient level flag forwhether the coefficient level of the transform coefficient is largerthan a fifth threshold value. Here, the significant coefficient flag maybe the sig_coeff_flag, the sign flag may be the ceff_sign_flag, thefirst coefficient level flag may be the abs_level_gt1_flag, and theparity level flag may be the par_level_flag. Further, the secondcoefficient level flag may be the abs_level_gt3_flag or theabs_level_gtx_flag, the third coefficient level flag may be theabs_level_gt5_flag or the abs_level_gtx_flag, the fourth coefficientlevel flag may be the abs_level_gt7_flag or the abs_level_gtx_flag, andthe fifth coefficient level flag may be the abs_level_gt9_flag or theabs_level_gtx_flag.

Further, for example, the bypass-coded syntax elements for the transformcoefficient may include coefficient level information for the value ofthe transform coefficient (or coefficient level) and/or a sign flagrepresenting the sign for the transform coefficient. The coefficientlevel information may be the abs_remainder and/or the dec_abs_level, andthe sign flag may be the ceff_sign_flag.

The encoding apparatus generates a bitstream including the dependentquantization enabled flag, the sign data hiding enabled flag, the TSRCenabled flag and the residual information (S1440). For example, theencoding apparatus may output image information including the dependentquantization enabled flag, the sign data hiding enabled flag, the TSRCenabled flag and the residual information as the bitstream. Thebitstream may include the dependent quantization enabled flag, the signdata hiding enabled flag, the TSRC enabled flag and the residualinformation. Also, the bitstream may further include the transform skipenabled flag.

Meanwhile, the image information may include prediction relatedinformation for the current block. The prediction related informationmay include prediction mode information for an inter prediction mode oran intra prediction mode performed on the current block.

Meanwhile, the bitstream may be transmitted to the decoding apparatusthrough a network or a (digital) storage medium. Here, the network mayinclude a broadcasting network and/or a communication network, and thedigital storage medium may include various storage media, such as USB,SD, CD, DVD, Blu-ray, HDD, and SSD.

FIG. 15 briefly illustrates an encoding apparatus for performing animage encoding method according to the present disclosure. The methoddisclosed in FIG. 14 may be performed by the encoding apparatusdisclosed in FIG. 15 . Specifically, for example, the entropy encoder ofthe encoding apparatus of FIG. 15 may perform S1400 to S1440 of FIG. 14. Further, although not illustrated, a process of deriving a predictionsample may be performed by the predictor of the encoding apparatus, aprocess of a residual sample for the current block based on the originalsample and the prediction sample for the current block may be performedby the subtractor of the encoding apparatus, and a process of generatinga reconstructed sample and a reconstructed picture for the current blockbased on the residual sample and the prediction sample for the currentblock may be performed by the adder of the encoding apparatus.

FIG. 16 briefly illustrates an image decoding method performed by adecoding apparatus according to the present disclosure. The methoddisclosed in FIG. 16 may be performed by the decoding apparatusdisclosed in FIG. 3 . Specifically, for example, S1600 to S1630 of FIG.16 may be performed by the entropy decoder of the decoding apparatus,S1640 of FIG. 16 may be performed by the residual processor of thedecoding apparatus, and S1650 of FIG. 16 may be performed by the adderof the decoding apparatus. Further, although not illustrated, a processof receiving prediction information for the current block may beperformed by the entropy decoder of the decoding apparatus, and aprocess of deriving a prediction sample of the current block may beperformed by the predictor of the decoding apparatus.

The decoding apparatus obtains a dependent quantization enabled flag forwhether dependent quantization is enabled (S1600). The decodingapparatus may obtain image information including the dependentquantization enabled flag through a bitstream. The image information mayinclude the dependent quantization enabled flag. For example, thedependent quantization enabled flag may be a flag for whether thedependent quantization is enabled. For example, the dependentquantization enabled flag may represent whether the dependentquantization is enabled. That is, for example, the dependentquantization enabled flag may represent whether the dependentquantization is enabled for blocks of pictures in a sequence. Forexample, the dependent quantization enabled flag may represent whether adependent quantization used flag representing whether the dependentquantization is used for a current slice may be present. For example,the dependent quantization enabled flag having a value of 1 mayrepresent that the dependent quantization is enabled, and the dependentquantization enabled flag having a value of 0 may represent that thedependent quantization is not enabled. Also, for example, the dependentquantization enabled flag may be signaled in an SPS syntax or a sliceheader syntax. The syntax element of the dependent quantization enabledflag may be the above-described sps_dep_quant_enabled_flag. Thesps_dep_quant_enabled_flag may be referred to assh_dep_quant_enabled_flag, sh_dep_quant_used_flag, orph_dep_quant_enabled_flag.

The decoding apparatus obtains a sign data hiding enabled flag forwhether sign data hiding is enabled (S1610). The decoding apparatus mayobtain image information including the sign data hiding enabled flagthrough a bitstream. The image information may include the sign datahiding enabled flag. For example, the sign data hiding enabled flag maybe a flag for whether the sign data hiding is enabled. For example, thesign data hiding enabled flag may represent whether the sign data hidingis enabled. That is, for example, the sign data hiding enabled flag mayrepresent whether the sign data hiding is enabled for blocks of picturesin a sequence. For example, the sign data hiding enabled flag mayrepresent whether a sign data hiding used flag representing whether thesign data hiding is used for a current slice may be present. Forexample, the sign data hiding enabled flag having a value of 1 mayrepresent that the sign data hiding is enabled, and the sign data hidingenabled flag having a value of 0 may represent that the sign data hidingis not enabled. For example, the sign data hiding enabled flag having avalue of 1 may represent that the sign data hiding used flag may bepresent, and the sign data hiding enabled flag having a value of 0 mayrepresent that the sign data hiding used flag is not present. Also, forexample, the sign data hiding enabled flag may be signaled in an SPSsyntax. Alternatively, for example, the sign data hiding enabled flagmay be signaled in a picture header syntax or a slice header syntax. Thesyntax element of the sign data hiding enabled flag may be thesps_sign_data_hiding_enabled_flag.

The decoding apparatus obtains a transform skip residual coding (TSRC)enabled flag for whether TSRC is enabled based on the dependentquantization enabled flag and the sign data hiding enabled flag (S1620).The image information may include the TSRC enabled flag.

For example, the decoding apparatus may obtain the TSRC enabled flagbased on the dependent quantization enabled flag and the sign datahiding enabled flag. For example, the TSRC enabled flag may be obtainedbased on the dependent quantization enabled flag having a value of 0 andthe sign data hiding enabled flag having a value of 0. That is, forexample, when a value of the dependent quantization enabled flag is 0(that is, the dependent quantization enabled flag represents that thedependent quantization is not enabled), and a value of the sign datahiding enabled flag is 0 (that is, the sign data hiding enabled flagrepresents that the sign data hiding is not enabled), the TSRC enabledflag may be obtained. In other words, for example, when a value of thedependent quantization enabled flag is 0 (that is, the dependentquantization enabled flag represents that the dependent quantization isnot enabled), and a value of the sign data hiding enabled flag is 0(that is, the sign data hiding enabled flag represents that the signdata hiding is not enabled), the TSRC enabled flag may be signaled.Also, for example, when the value of the sign data hiding enabled flagis 1, the TSRC enabled flag may not be obtained, and a value of the TSRCenabled flag may be derived as 0. That is, for example, when the valueof the sign data hiding enabled flag is 1, the TSRC enabled flag may notbe signaled, and a value of the TSRC enabled flag may be derived as 0.Also, for example, when the value of the dependent quantization enabledflag is 1, the TSRC enabled flag may not be obtained, and a value of theTSRC enabled flag may be derived as 0. That is, for example, when thevalue of the dependent quantization enabled flag is 1 (eg, when thedependent quantization is applied (or used) to the current block), theTSRC enabled flag may not be signaled, and a value of the TSRC enabledflag may be derived as 0. Thus, for example, when the dependentquantization and the sign data hiding are not enabled for the currentblock, the TSRC enabled flag may be signaled (or obtained). When thedependent quantization and/or sign data hiding is enabled for thecurrent block, the TSRC enabled flag may not be signaled (or obtained),and the value of the TSRC enabled flag may be derived as 0. Here, thecurrent block may be a Coding Block (CB) or a Transform Block (TB).

Here, for example, the TSRC enabled flag may be a flag for whether theTSRC is enabled. That is, for example, the TSRC enabled flag may a flagrepresenting whether the TSRC is enabled for blocks in a slice. Forexample, the TSRC enabled flag having a value of 1 may represent thatthe TSRC is not enabled, and the TSRC enabled flag having a value of 0may represent that the TSRC is enabled. Also, for example, the TSRCenabled flag may be signaled in a slice header syntax. The syntaxelement of the TSRC enabled flag may be the above-describedsh_ts_residual_coding_disabled_flag.

Meanwhile, for example, the decoding apparatus may obtain a transformskip enabled flag. The decoding apparatus may image informationincluding the transform skip enabled flag through the bitstream. Imageinformation may include the transform skip enabled flag. Here, thecurrent block may be a coding block (CB) or a transform block (TB). Forexample, the transform skip enabled flag may be a flag for whether thetransform skip is enabled. For example, the transform skip enabled flagmay represent whether the transform skip is enabled. That is, forexample, the transform skip enabled flag may represent whether thetransform skip is enabled for the blocks of the pictures in thesequence. For example, the transform skip enabled flag may representwhether the transform skip flag can be present. For example, thetransform skip enabled flag having the value of 1 may represent that thetransform skip is enabled, and the transform skip enabled flag havingthe value of 0 may represent that the transform skip is not enabled.That is, for example, the transform skip enabled flag having the valueof 1 may represent that the transform skip flag can be present, and thetransform skip enabled flag having the value of 0 may represent that thetransform skip flag is not present. Further, for example, the transformskip enabled flag may be signaled to a sequence parameter set (SPS)syntax. The syntax element of the transform skip enabled flag may be theabove-described sps_transform_skip_enabled_flag.

Further, for example, the TSRC enabled flag may be obtained based on thesign data hiding enabled flag, the dependent quantization enabled flag,and/or the transform skip enabled flag. For example, the TSRC enabledflag may be obtained based on the sign data hiding enabled flag having avalue of 0, the dependent quantization enabled flag having a value of 0,and the transform skip enabled flag having a value of 1. That is, forexample, when a value of the sign data hiding enabled flag is 0 (thatis, the sign data hiding enabled flag represents that sign data hidingis not enabled), a value of the dependent quantization enabled flag is 0(that is, the dependent quantization enabled flag represents thatdependent quantization is not enabled), and a value of the transformskip enabled flag is 1 (that is, the transform skip enabled flagrepresents that transform skip is enabled), the TSRC The enabled flagmay be obtained (or signaled). Also, for example, when the value of thedependent quantization enabled flag is 1, the TSRC enabled flag may notbe obtained, and the value of the TSRC enabled flag may be derived as 0.That is, for example, when the value of the dependent quantizationenabled flag is 1, the TSRC enabled flag may not be signaled, and thevalue of the TSRC enabled flag may be derived as 0. Also, for example,when the value of the transform skip enabled flag is 0, the TSRC enabledflag may not be obtained, and the value of the TSRC enabled flag may bederived as 0. That is, for example, when the value of the transform skipenabled flag is 0, the TSRC enabled flag may not be signaled, and thevalue of the TSRC enabled flag may be derived as 0.

The decoding apparatus obtains residual information for a current blockbased on the TSRC enabled flag (S1630). The decoding may obtain residualinformation for a current block based on the TSRC enabled flag.

For example, the decoding apparatus may determine a residual codingsyntax for the current block based on the TSRC enabled flag. Forexample, the decoding apparatus may determine the residual coding syntaxfor the current block as one of a regular residual coding (RRC) syntaxand a transform skip residual coding (TSRC) syntax based on the TSRCenabled flag. The RRC syntax may represent a syntax according to RRC,and the TSRC syntax may represent a syntax according to the TSRC.

For example, based on the TSRC enabled flag having the value of 1, theresidual coding syntax for the current block may be determined as theregular residual coding (RRC) syntax. In this case, for example, atransform skip flag for whether transform skip is applied to the currentblock may be obtained based on the transform skip enabled flag having avalue of 1, and the value of the transform skip flag may be 1. Forexample, the image information may include the transform skip flag forthe current block. The transform skip flag may represent whether thecurrent block is the transform skip block. That is, the transform skipflag may represent whether the transform has been applied to thetransform coefficients of the current block. The syntax elementrepresenting the transform skip flag may be the transform skip flag asdescribed above. For example, if the value of the transform skip flag is1, the transform skip flag may represent that the transform has not beenapplied to the current block (i.e., transform skipped), whereas if thevalue of the transform skip flag is 0, the transform skip flag mayrepresent that the transform has been applied to the current block. Forexample, if the current block is the transform skip block, the value ofthe transform skip flag for the current block may be 1.

Further, for example, based on the TSRC enabled flag having the value of0, the residual coding syntax for the current block may be determined asthe transform skip residual coding (TSRC) syntax. Further, for example,the transform skip flag for whether transform skip is applied to thecurrent block may be obtained, and based on the transform skip flaghaving the value of 1 and the TSRC enabled flag having the value of 0,the residual coding syntax for the current block may be determined asthe transform skip residual coding (TSRC) syntax. Further, for example,the transform skip flag for whether transform skip is applied to thecurrent block may be obtained, and based on the transform skip flaghaving the value of 0 and the TSRC enabled flag having the value of 0,the residual coding syntax for the current block may be determined asthe regular residual coding (RRC) syntax.

Thereafter, for example, the decoding apparatus may obtain the residualinformation of the determined residual coding syntax for the currentblock. For example, residual information of the regular residual coding(RRC) syntax may be obtained based on the TSRC enabled flag having thevalue of 1, and residual information of the TSRC syntax may be obtainedbased on the TSRC enabled flag having the value of 0. The imageinformation may include the residual information.

For example, if the residual coding syntax for the current block isdetermined as the RRC syntax, the decoding apparatus may obtain theresidual information of the RRC syntax for the current block. Forexample, the residual information of the RRC syntax may include thesyntax elements disclosed in Table 2 as described above.

For example, the residual information of the RRC syntax may include thesyntax elements for the transform coefficient of the current block.Here, the transform coefficient may be represented as the residualcoefficient.

For example, the syntax elements may include syntax elements, such aslast_sig_coeff_x_prefix, last_sig_coeff_y_prefix,last_sig_coeff_x_suffix, last_sig_coeff_y_suffix, sb_coded_flag,sig_coeff_flag, par_level_flag, abs_level_gtX_flag (e.g.,abs_level_gtx_flag[n][0] and/or abs_level_gtx_flag[n][1]),abs_remainder, dec_abs_level, and/or coeff_sign_flag.

Specifically, for example, the syntax elements may include positioninformation representing the position of the last non-zero transformcoefficient in a residual coefficient array of the current block. Thatis, the syntax elements may include the position informationrepresenting the position of the last non-zero transform coefficient inthe scanning order of the current block. The position information mayinclude information representing a prefix in a column position of thelast non-zero transform coefficient, information representing a prefixin a row position of the last non-zero transform coefficient,information representing a suffix of the column position of the lastnon-zero transform coefficient, and information representing a suffix inthe row position of the last non-zero transform coefficient. The syntaxelements for the position information may be last_sig_coeff_x_prefix,last_sig_coeff_y_prefix, last_sig_coeff_x_suffix, andlast_sig_coeff_y_suffix. Meanwhile, the non-zero transform coefficientmay be called a significant coefficient.

Further, for example, the syntax elements may include a coded subblockflag representing whether the current subblock of the current blockincludes the non-zero transform coefficient, a significant coefficientflag representing whether the transform coefficient of the current blockis the non-zero transform coefficient, a first coefficient level flagfor whether the coefficient level for the transform coefficient islarger than a first threshold value, a parity level flag for a parity ofthe coefficient level, and/or a second coefficient level flag forwhether the coefficient level of the transform coefficient is largerthan a second threshold value. Here, the coded subblock flag may be thesb_coded_flag or coded_sub_block_flag, the significant coefficient flagmay be the sig_coeff_flag, the first coefficient level flag may be theabs_level_gt1_flag or the abs_level_gtx_flag, the parity level flag maybe the par_level_flag, and the second coefficient level flag may be theabs_level_gt3_flag or the abs_level_gtx_flag.

Further, for example, the syntax elements may include coefficient valuerelated information for the transform coefficient value of the currentblock. The coefficient value related information may be an abs_remainderand/or a dec_abs_level.

Further, for example, the syntax elements may include a sign flagrepresenting the sign of the transform coefficient. The sign flag may bethe coeff_sign_flag.

Meanwhile, for example, when the sign data hiding is applied to thecurrent block, a sign flag of a first significant transform coefficientof a current coefficient group (CG) in the current block may be notsignaled. That is, for example, when the sign data hiding is applied tothe current block, the syntax elements may not include a sign flagrepresenting a sign of the first significant transform coefficient.Meanwhile, for example, whether the sign data hiding is applied to thecurrent block may be derived based on the sign data hiding enabled flagand/or a position of the first significant transform coefficient and aposition of the last significant transform coefficient of the currentCG. For example, when a value of the sign data hiding enabled flag is 1,and a value obtained by subtracting the position of the firstsignificant transform coefficient from the position of the lastsignificant transform coefficient is greater than 3, (that is, when avalue of the sign data hiding enabled flag is 1, and a number ofsignificant transform coefficients in the current CG is greater than 3),the sign data hiding may be applied to the current CG of the currentblock.

Further, for example, if the residual coding syntax for the currentblock is determined as the TSRC syntax, the decoding apparatus mayobtain the residual information of the TSRC syntax for the currentblock. For example, the residual information of the TSRC syntax mayinclude the syntax elements disclosed in Table 3 as described above.

For example, the residual information of the TSRC syntax may include thesyntax elements for the transform coefficient of the current block.Here, the transform coefficient may be represented as the residualcoefficient.

For example, the syntax elements may include context-coded syntaxelements for the transform coefficient and/or bypass-coded syntaxelements. The syntax elements may include the syntax elements, such assig_coeff_flag, coeff_sign_flag, par_level_flag, abs_level_gtX_flag(e.g., abs_level_gtx_flag[n][0], abs_level_gtx_flag[n][1],abs_level_gtx_flag[n][2], abs_level_gtx_flag[n][3], and/orabs_level_gtx_flag[n][4]), abs_remainder, and/or coeff_sign_flag.

For example, the context-coded syntax elements for the transformcoefficient may include a significant coefficient flag representingwhether the transform coefficient is the non-zero transform coefficient,a sign flag representing the sign for the transform coefficient, a firstcoefficient level flag for whether the coefficient level for thetransform coefficient is larger than a first threshold value, and/or aparity level flag for the parity of the transform level for thetransform coefficient. Further, for example, the context-coded syntaxelements may include a second coefficient level flag for whether thecoefficient level of the transform coefficient Further, for example, thecontext-coded syntax elements may include a second coefficient levelflag for whether the coefficient level of the transform coefficient islarger than a second threshold value, a third coefficient level flag forwhether the coefficient level of the transform coefficient is largerthan a third threshold value, a fourth coefficient level flag forwhether the coefficient level of the transform coefficient is largerthan a fourth threshold value, and/or a fifth coefficient level flag forwhether the coefficient level of the transform coefficient is largerthan a fifth threshold value. Here, the significant coefficient flag maybe the sig_coeff_flag, the sign flag may be the ceff_sign_flag, thefirst coefficient level flag may be the abs_level_gt1_flag, and theparity level flag may be the par_level_flag. Further, the secondcoefficient level flag may be the abs_level_gt3_flag or theabs_level_gtx_flag, the third coefficient level flag may be theabs_level_gt5_flag or the abs_level_gtx_flag, the fourth coefficientlevel flag may be the abs_level_gt7_flag or the abs_level_gtx_flag, andthe fifth coefficient level flag may be the abs_level_gt9_flag or theabs_level_gtx_flag.

Further, for example, the bypass-coded syntax elements for the transformcoefficient may include coefficient level information for the value ofthe transform coefficient (or coefficient level) and/or a sign flagrepresenting the sign for the transform coefficient. The coefficientlevel information may be the abs_remainder and/or the dec_abs_level, andthe sign flag may be the ceff_sign_flag.

The decoding apparatus derives a residual sample of the current blockbased on the residual information (S1640). For example, the decodingapparatus may derive transform coefficients of the current block basedon the residual information, and may derive residual samples of thecurrent block base on the transform coefficients.

For example, the decoding apparatus may derive the transformcoefficients of the current block based on the syntax elements of theresidual information. Thereafter, the decoding apparatus may derive theresidual samples of the current block based on the transformcoefficients. As an example, if it is derived that the transform is notapplied for the current block based on the transform skip flag, that is,if the value of the transform skip flag is 1, the decoding apparatus mayderive the transform coefficients as the residual samples of the currentblock. Further, for example, if it is derived that the transform is notapplied for the current block based on the transform skip flag, that is,if the value of the transform skip flag is 1, the decoding apparatus mayderive the residual samples of the current block by dequantizing thetransform coefficients. Further, for example, if it is derived that thetransform is applied for the current block based on the transform skipflag, that is, if the value of the transform skip flag is 0, thedecoding apparatus may derive the residual samples of the current blockby performing inverse transform of the transform coefficients. Further,for example, if it is derived that the transform is applied for thecurrent block based on the transform skip flag, that is, if the value ofthe transform skip flag is 0, the decoding apparatus may derive theresidual samples of the current block by dequantizing the transformcoefficients and performing inverse transform of the dequantizedtransform coefficients.

Meanwhile, in case that the dependent quantization is applied for thecurrent block, the decoding apparatus may derive the residual samples ofthe current block by performing the dependent quantization process forthe transform coefficients. For example, in case that the dependentquantization is applied for the current block, the decoding apparatusmay update the state (Qstate) for the dependent quantization based onthe coefficient level of the transform coefficient just before thecurrent transform coefficient in the scanning order, may derive thecoefficient level of the current transform coefficient based on theupdated state and the syntax elements for the current transformcoefficient, and may derive the residual sample by dequantizing thederived coefficient level. For example, the current transformcoefficient may be dequantized based on the quantization parameter for areconstructed level of the current transform coefficient in a scalarquantizer for the updated state. Here, the reconstructed level may bederived based on the syntax elements for the current transformcoefficient.

Meanwhile, for example, when the sign data hiding is applied to thecurrent block, a sign of a first significant transform coefficient ofthe current CG in the current block may be derived based on the sum ofabsolute values of significant transform coefficients in the current CG.For example, when the sum of the absolute values of the significanttransform coefficients is even, the sign of the first significanttransform coefficient may be derived as a positive value, and when thesum of the absolute values of the significant transform coefficients isodd, the sign of the first significant transform coefficient may bederived as a negative value.

The decoding apparatus generates a reconstructed picture based on theresidual sample (S1650). For example, the decoding apparatus maygenerate the reconstructed sample and/or reconstructed picture of thecurrent block based on the residual sample. For example, the decodingapparatus may derive a prediction sample by performing an interprediction mode or an intra prediction mode on the current block basedon prediction information received through the bitstream, and maygenerate the reconstructed sample through addition of the predictionsample and the residual sample to each other.

Thereafter, as needed, in order to enhance the subjective/objectivepicture quality, an in-loop filtering procedure, such as deblockingfiltering, SAO and/or ALF procedure, may be applied to the reconstructedpicture as described above.

FIG. 17 briefly illustrates a decoding apparatus for performing an imagedecoding method according to the present disclosure. The methoddisclosed in FIG. 16 may be performed by the decoding apparatusdisclosed in FIG. 17 . Specifically, for example, the entropy decoder ofthe decoding apparatus of FIG. 17 may perform S1600 to S1630, theresidual processor of the decoding apparatus of FIG. 17 may performS1640 of FIG. 16 , and the adder of the decoding apparatus of FIG. 17may perform S1650 of FIG. 16 . Further, although not illustrated, aprocess of receiving prediction information for the current block may beperformed by the entropy decoder of the decoding apparatus of FIG. 17 ,and a process of deriving a prediction sample of the current block maybe performed by the predictor of the decoding apparatus of FIG. 17 .

According to the present disclosure, the residual coding efficiency canbe enhanced.

Further, according to the present disclosure, the TSRC enabled flag canbe signaled when the sign data hiding is not enabled by setting thesignaling relationship between the sign data hiding enabled flag and theTSRC enabled flag, through this, when the RRC syntax is coded for thetransform skip block because the TSRC is not enabled, sign data hidingis not used to improve coding efficiency, and the overall residualcoding efficiency can be improved through reduction of the amount ofbits being coded.

Further, according to the present disclosure, the signaling relationshipbetween the dependent quantization enabled flag and the TSRC enabledflag can be established, and if the dependent quantization is notenabled, the TSRC enabled flag can be signaled, and through this, if theTSRC is not enabled and then the RRC syntax is coded for the transformskip block, the dependent quantization is not to be used, so that thecoding efficiency can be improved, and the overall residual codingefficiency can be improved through the reduction of the amount of bitsbeing coded.

Further, according to the present disclosure, the signaling relationshipbetween the transform skip enabled flag and the TSRC enabled flag can beestablished, and if the transform skip is enabled, the TSRC enabled flagcan be signaled, and through this, the overall residual codingefficiency can be improved through the reduction of the amount of bitsbeing coded.

In the above-described embodiment, the methods are described based onthe flowchart having a series of steps or blocks. The present disclosureis not limited to the order of the above steps or blocks. Some steps orblocks may occur simultaneously or in a different order from other stepsor blocks as described above. Further, those skilled in the art willunderstand that the steps shown in the above flowchart are notexclusive, that further steps may be included, or that one or more stepsin the flowchart may be deleted without affecting the scope of thepresent disclosure.

The embodiments described in this specification may be performed bybeing implemented on a processor, a microprocessor, a controller or achip. For example, the functional units shown in each drawing may beperformed by being implemented on a computer, a processor, amicroprocessor, a controller or a chip. In this case, information forimplementation (e.g., information on instructions) or algorithm may bestored in a digital storage medium.

In addition, the decoding apparatus and the encoding apparatus to whichthe present disclosure is applied may be included in a multimediabroadcasting transmission/reception apparatus, a mobile communicationterminal, a home cinema video apparatus, a digital cinema videoapparatus, a surveillance camera, a video chatting apparatus, areal-time communication apparatus such as video communication, a mobilestreaming apparatus, a storage medium, a camcorder, a VoD serviceproviding apparatus, an Over the top (OTT) video apparatus, an Internetstreaming service providing apparatus, a three-dimensional (3D) videoapparatus, a teleconference video apparatus, a transportation userequipment (e.g., vehicle user equipment, an airplane user equipment, aship user equipment, etc.) and a medical video apparatus and may be usedto process video signals and data signals. For example, the Over the top(OTT) video apparatus may include a game console, a blue-ray player, aninternet access TV, a home theater system, a smart phone, a tablet PC, aDigital Video Recorder (DVR), and the like.

Furthermore, the processing method to which the present disclosure isapplied may be produced in the form of a program that is to be executedby a computer and may be stored in a computer-readable recording medium.Multimedia data having a data structure according to the presentdisclosure may also be stored in computer-readable recording media. Thecomputer-readable recording media include all types of storage devicesin which data readable by a computer system is stored. Thecomputer-readable recording media may include a BD, a Universal SerialBus (USB), ROM, PROM, EPROM, EEPROM, RAM, CD-ROM, a magnetic tape, afloppy disk, and an optical data storage device, for example.Furthermore, the computer-readable recording media includes mediaimplemented in the form of carrier waves (e.g., transmission through theInternet). In addition, a bit stream generated by the encoding methodmay be stored in a computer-readable recording medium or may betransmitted over wired/wireless communication networks.

In addition, the embodiments of the present disclosure may beimplemented with a computer program product according to program codes,and the program codes may be performed in a computer by the embodimentsof the present disclosure. The program codes may be stored on a carrierwhich is readable by a computer.

FIG. 18 illustrates a structural diagram of a contents streaming systemto which the present disclosure is applied.

The content streaming system to which the embodiment(s) of the presentdisclosure is applied may largely include an encoding server, astreaming server, a web server, a media storage, a user device, and amultimedia input device.

The encoding server compresses content input from multimedia inputdevices such as a smartphone, a camera, a camcorder, etc. Into digitaldata to generate a bitstream and transmit the bitstream to the streamingserver. As another example, when the multimedia input devices such assmartphones, cameras, camcorders, etc. directly generate a bitstream,the encoding server may be omitted.

The bitstream may be generated by an encoding method or a bitstreamgenerating method to which the embodiment(s) of the present disclosureis applied, and the streaming server may temporarily store the bitstreamin the process of transmitting or receiving the bitstream.

The streaming server transmits the multimedia data to the user devicebased on a user's request through the web server, and the web serverserves as a medium for informing the user of a service. When the userrequests a desired service from the web server, the web server deliversit to a streaming server, and the streaming server transmits multimediadata to the user. In this case, the content streaming system may includea separate control server. In this case, the control server serves tocontrol a command/response between devices in the content streamingsystem.

The streaming server may receive content from a media storage and/or anencoding server. For example, when the content is received from theencoding server, the content may be received in real time. In this case,in order to provide a smooth streaming service, the streaming server maystore the bitstream for a predetermined time.

Examples of the user device may include a mobile phone, a smartphone, alaptop computer, a digital broadcasting terminal, a personal digitalassistant (PDA), a portable multimedia player (PMP), navigation, a slatePC, tablet PCs, ultrabooks, wearable devices (ex. Smartwatches, smartglasses, head mounted displays), digital TVs, desktops computer, digitalsignage, and the like. Each server in the content streaming system maybe operated as a distributed server, in which case data received fromeach server may be distributed.

The claims described in the present disclosure may be combined invarious ways. For example, the technical features of the method claimsof the present disclosure may be combined to be implemented as anapparatus, and the technical features of the apparatus claims of thepresent disclosure may be combined to be implemented as a method. Inaddition, the technical features of the method claim of the presentdisclosure and the technical features of the apparatus claim may becombined to be implemented as an apparatus, and the technical featuresof the method claim of the present disclosure and the technical featuresof the apparatus claim may be combined to be implemented as a method.

What is claimed is:
 1. An image decoding method performed by a decodingapparatus, the method comprising: obtaining a dependent quantizationenabled flag for whether dependent quantization is enabled; obtaining asign data hiding enabled flag for whether sign data hiding is enabled;obtaining a Transform Skip Residual Coding (TSRC) enabled flag forwhether TSRC is enabled based on the dependent quantization enabled flagand the sign data hiding enabled flag; obtaining residual informationfor a current block based on the TSRC enabled flag; deriving a residualsample of the current block based on the residual information; andgenerating a reconstructed picture based on the residual sample, whereinthe TSRC enabled flag is obtained based on the dependent quantizationenabled flag having a value of 0 and the sign data hiding enabled flaghaving a value of
 0. 2. The image decoding method of claim 1, whereinthe sign data hiding enabled flag having the value of 1 represents thatthe sign data hiding is enabled, wherein the sign data hiding enabledflag having the value of 0 represents that the sign data hiding is notenabled.
 3. The image decoding method of claim 1, wherein the dependentquantization enabled flag having the value of 1 represents that thedependent quantization is enabled, wherein the dependent quantizationenabled flag having the value of 0 represents that the dependentquantization is not enabled.
 4. The image decoding method of claim 1,wherein the TSRC enabled flag having a value of 1 represents that theTSRC is not enabled, wherein the TSRC enabled flag having the value of 0represents that the TSRC is enabled.
 5. The image decoding method ofclaim 1, wherein when the dependent quantization is not enabled for thecurrent block, and the sign data hiding is not enabled for the currentblock, the TSRC enabled flag is obtained.
 6. The image decoding methodof claim 1, wherein when the sign data hiding is applied to the currentblock, the TSRC enabled flag is not obtained, and a value of the TSRCenabled flag is derived as
 0. 7. The image decoding method of claim 6,wherein when the sign data hiding is applied to the current block, asign of a first significant transform coefficient of a currentcoefficient group (CG) in the current block is derived based on a sum ofabsolute values of significant transform coefficients in the current CG.8. The image decoding method of claim 7, wherein when the sign datahiding is applied to the current block, the residual information doesnot include a sign flag for the first significant transform coefficient.9. The image decoding method of claim 4, wherein residual information ofa regular residual coding (RRC) syntax is obtained based on the TSRCenabled flag having the value of
 1. 10. The image decoding method ofclaim 9, wherein a transform skip flag for whether transform skip isapplied to the current block is obtained, and a value of the transformskip flag is
 1. 11. The image decoding method of claim 4, wherein whenthe current block is a transform skip block, and the value of the TSRCenabled flag is 0, the residual information for the current block isresidual information of a TSRC syntax.
 12. The image decoding method ofclaim 11, wherein the residual information of the TSRC syntax includescontext-coded syntax elements for a transform coefficient, wherein thecontext-coded syntax elements include a significant coefficient flagrepresenting whether the transform coefficient is a non-zero transformcoefficient, a parity level flag for a parity of a coefficient level forthe transform coefficient, a sign flag representing a sign for thetransform coefficient, a first coefficient level flag for whether thecoefficient level is larger than a first threshold value, and a secondcoefficient level flag for whether the coefficient level of thetransform coefficient is larger than a second threshold value.
 13. Theimage decoding method of claim 1, wherein when the dependentquantization is applied to the current block, the TSRC enabled flag isnot obtained, and a value of the TSRC enabled flag is derived as
 0. 14.An image encoding method performed by an encoding apparatus, the methodcomprising: encoding a dependent quantization enabled flag for whetherdependent quantization is enabled; encoding a sign data hiding enabledflag for whether sign data hiding is enabled; encoding a Transform SkipResidual Coding (TSRC) enabled flag for whether TSRC is enabled based onthe dependent quantization enabled flag and the sign data hiding enabledflag; encoding residual information for a current block based on theTSRC enabled flag; and generating a bitstream including the dependentquantization enabled flag, the sign data hiding enabled flag, the TSRCenabled flag and the residual information, wherein the TSRC enabled flagis encoded based on the dependent quantization enabled flag having avalue of 0 and the sign data hiding enabled flag having a value of 0.15. A non-transitory computer-readable storage medium storing abitstream including image information causing a decoding apparatus toperform an image decoding method, the image decoding method comprising:obtaining a dependent quantization enable flag for whether dependentquantization is enable; obtaining a sign data hiding enable flag forwhether sign data hiding is enable; obtaining a Transform Skip ResidualCoding (TSRC) enable flag for whether TSRC is enable based on thedependent quantization enable flag and the sign data hiding enable flag;obtaining residual information for a current block based on the TSRCenable flag; deriving a residual sample of the current block based onthe residual information; and generating a reconstructed picture basedon the residual sample, wherein the TSRC enable flag is obtained basedon the dependent quantization enable flag having a value of 0 and thesign data hiding enable flag having a value of 0.